Semesterübersicht – letztes Semester

Semesterübersicht Wintersemester 2019/2020

Wintersemester 2019/2020 - Sommersemester 2020 - Wintersemester 2020/2021

08 Oct 2019

Institut für KernphysikSonderseminar: 14:15 Uhr s.t., HS Kernphysik, Becherweg 45
 Garth Huber, University of Regina, Regina, Saskatchewan, Canada see attached pdf Sonderseminar
10 Oct 2019

Seminar über Theorie der kondensierten Materie / TRR146 Seminar

K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Christoph Ortner, University of Warwick Accurate molecular simulation requires computationally expensive quantum chemistry models that makes simulating complex material phenomena or large molecules intractable. The past decade has seen a revival of interatomic potentials (IPs), fast but traditionally inaccurate surrogate models, re-casting their construction as an approximation and data-fitting problem. I will give an introduction to this problem, from a mixed modelling / data / mathematics perspective. In particular I want to show how it can be formalised as a high-dimensional approximation problem, with many structures that can be exploited to make it tractable. I will introduce two approximation schemes, both using different symmetric polynomials, targeting in particular efficiency and transferability, some preliminary simulation results, and the beginnings of a rigorous numerical analysis. Joint work with Geneviève Dusson (CNRS Besançon), Markus Bachmayr (Mainz), Gabor Csanyi and Cas van der Oord (Cambridge), Simon Etter (NU Singapur).

Seminar über Theorie der kondensierten Materie / TRR146 Seminar

K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau11:15 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Genevive Dusson, University of Warwick I will present the practical construction of interatomic potentials for materials and molecules based on a body-order expansion (ANOVA, HDRM), each body order being represented by polynomials satisfying the rotation and permutation symmetry of the "exact" potential energy surface. These polynomials are determined in a data-driven fashion from linear fits trained with ab initio data. I will report convergence tests on training sets for materials and molecules, illustrating the accuracy, the low computational cost, and the systematic improvability of the potential. I will then outline a range of the regularisation procedures that we incorporate into the polynomial fits to achieve transferability of the potentials. Finally, I will outline a testing framework to stress-test the generalisation capabilities of new potentials far from the training set. Joint work with Alice Allen (Cambridge), Gbor Csnyi (Cambridge), Christoph Ortner (Warwick), and Cas van der Oord (Cambridge).
15 Oct 2019

Theorie-Palaver

Institut für Physik14:30 Uhr s.t., Socialroom
 Fatemeh Elahi, IPM, Tehran A few hundred cold gas clouds were recently discovered, each situated a few hundred parsecs from the center of the Milky Way Galaxy. These gas clouds can provide unprecedented sensitivity to dark matter-standard model interactions. The main physical basis is simple: dark matter tends to have a higher temperature than the coldest interstellar and intergalactic gas. Therefore, dark matter can heat the gas to higher-than-observed temperatures, if dark matter interacts enough with baryons or electrons in the gas cloud. In this talk, I will discuss the bounds cold gas clouds give on ultra-light dark photon, vector portal, and millicharged dark matter.

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
 Professor Wick Haxton, Department of Physics, Berkeley There is a great deal of experimental effort being invested in laboratory searches for heavy dark matter particles, where the signal is a recoiling nucleus produce by dark matter elastic scattering. An interesting question is the number of experiments that will need to be done to ensure that the available discovery space has been adequately covered. Post discovery, a related question will be the number of independent experiment that will need to be completed, to fully characterize the interaction. I will describe an approach based on effective theory that allows one to address these and other questions.
21 Oct 2019

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
 Dr. John M. Schwantes, Pacific Northwest National Laboratory , Richland, WA, USA The young science of nuclear forensics was born out of a response to discoveries of weapons-usable nuclear Materials Out of Regulatory Control (MORC) in northern Europe in the early 1990s. This science not only supports law enforcement response to MORC events but represents a key component of nuclear security for any nation with nuclear or radiological materials holdings. Since the birth of nuclear forensic science, efforts like the Nuclear Security Summit, the Global Initiative to Combat Nuclear Terrorism, as well as those by the International Atomic Energy Agency and the Nuclear Forensics International Technical Working Group have strengthened nuclear forensics capabilities worldwide. Here, the capabilities and limitations of nuclear forensic science are described and several examples of applications of nuclear forensics in support of emergency response, law enforcement, and national security are provided.

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
J. Diefenbach, Mainz

22 Oct 2019

Theorie-Palaver

Institut für Physik14:30 Uhr s.t., MITP seminar room
 Andreas Helset, Bohr Institute We formulate an effective field theory describing large mass scalars and fermions minimally coupled to gravity. The operators of this effective field theory are organized in powers of the transfer momentum divided by the mass of the matter field, an expansion which lends itself to the efficient extraction of classical contributions from loop amplitudes in both the post-Newtonian and post-Minkowskian regimes. We use this effective field theory to calculate the classical and leading quantum gravitational scattering amplitude of two heavy spin-1/2 particles at the second post-Minkowskian order.

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Andreas Burkert, Faculty of Physics, LMU Munich

24 Oct 2019

Seminar über Theorie der kondensierten Materie / TRR146 Seminar

K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:15 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Joerg Steinkamp, ZDV, Uni Mainz
Research data management and data archiving at ZDV/JGU with iRODS

28 Oct 2019

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
O. Javier Hernandez, Mainz

Seminar about Experimental Particle and Astroparticle Physics (ETAP)

Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Michael Goedel, Institut für Physik

Masterkolloqium

29 Oct 2019

Theorie-Palaver

Institut für Physik14:30 Uhr s.t., MITP seminar room
 Alexey Vladimirov, Regensburg University The evolution of transverse momentum dependent distributions or TMD-evolution differs from ordinary renormalization group evolution in several aspects. Two main ones are its double-scale nature and the presence of non-perturbative component. In the talk, I review the recent progress in studies of TMD-evolution, including the proof of rapidity-divergence renormalization, soft-rapidity correspondence, zeta-prescription, and comparison with the experimental measurements.

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Rupert Huber, Institut für Physik, Universität Regensburg

30 Oct 2019

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Verena Spatz, TU Darmstadt Physics Education It is a widely held view that in the field of physics education the implementation of scientific findings into instruction practice should be a critical issue, however the record of research results on genuine classroom activities is generally poor. In the seminar, a project will be presented, that aims at closing this research-practice gap. In the project, novel teaching units on the introduction to Newtonian mechanics were developed and evaluated, based on empirical studies concerning common pre-instruction ideas, which students bring along into school. Some of these ideas are appropriate, whereas many are inappropriate to build upon in physics lessons. A very popular erroneous idea about motion is that a force is needed to keep an object moving at constant velocity. This novices concept has to be changed into an experts concept, that a force is needed only to change the velocity of an object. As illustrated in this example, teaching and learning physics often requires conceptual change. Considering this, the content area itself had to be restructured and teaching materials had to be prepared to meet students learning needs. An accompanying quasi-experimental field study with grade seven classes showed a significant improvement of students conceptual understanding.
31 Oct 2019

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Stephen D. Hogan, Department of Physics and Astronomy, University College London, UK Rydberg states, the bound quantum states of an attractive 1/r potential, play a central role in many precision spectroscopic tests of fundamental physics with atoms and molecules, e.g., [1,2]. As perhaps the simplest Rydberg system, the positronium atom - composed of an electron bound to its antiparticle the positron, and therefore a purely leptonic system described almost entirely by bound state QED theory - offers unique opportunities for studies of this kind. However, because of its short ground-state annihilation lifetime (142 ns) many precision experiments with positronium must be performed with longer-lived excited states - Rydberg states. The efficient preparation of Rydberg states in positronium is now possible following developments in positron beam and trap technologies [3], and the motion of the atoms excited to these states can be controlled and manipulated using inhomogeneous electric fields through the methods of Rydberg-Stark deceleration [4]. In this talk I will describe new precision microwave spectroscopic measurements of the triplet n=2 fine structure in positronium that takes advantage of these developments. I will also present a new technique for performing matter-wave interferometry with atoms in Rydberg states that has been developed using helium atoms [5], but in the future could be exploited for accurate gravity measurements with Rydberg positronium. [1] A. Beyer, L. Maisenbacher, A. Matveev, R. Pohl, K. Khabarova, A. Grinin, T. Lamour, D. C. Yost, Th. W. Hänsch, N. Kolachevsky, and Th. Udem, The Rydberg constant and proton size from atomic hydrogen, Science 358, 79 (2017) [2] N. Hölsch, M. Beyer, E. J. Salumbides, K. S. E. Eikema, W. Ubachs, Ch. Jungen, and F. Merkt, Benchmarking Theory with an Improved Measurement of the Ionization and Dissociation Energies of H2, Phys. Rev. Lett. 122, 103002 (2019) [3] T. E. Wall, A. M. Alonso, B. S. Cooper, A. Deller, S. D. Hogan, and D. B. Cassidy, Selective Production of Rydberg-Stark States of Positronium, Phys. Rev. Lett. 114, 173001 (2015) [4] S. D. Hogan, Rydberg-Stark deceleration of atoms and molecules, EPJ Techniques and Instrumentation 3, 1 (2016) [5] J. E. Palmer and S. D. Hogan, Electric Rydberg-atom interferometry, Phys. Rev. Lett. 122, 250404 (2019)
04 Nov 2019

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Laura Moschini, Brüssel
Dissociation of exotic nuclei at high energy

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Sascha Rau, Max-Planck-Institut für Kernphysik, Heidelberg

05 Nov 2019

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
 Special Colloquium in Memory of Professor Ernst Otten, Mainz Prof. Dr. Michèle Leduc, Laboratoire Kastler-Brossel, Ecole Normale Supérieure, Paris "Optical pumping of Helium-3 and MRI lung imaging"

Prof. Dr. Wilfried Nörtershäuser, Technische Universität Darmstadt "Atomic spectroscopy and nuclear structure"

Prof. Dr. Christian Weinheimer, Universität Münster "The search for the neutrino mass"

Prof. Dr. Werner Heil, Universität Mainz "Ernst Otten’s Persönlichkeit - Prägung und Wirken der WA EXAKT unter seiner Leitung"

Please notice different time and location: Staudinger Lecture Hall/Foyer, Max-Planck Institute for Polymer Research, Ackermann Weg 10, Tea from 3.00pm

Theorie-Palaver

Institut für Physik14:30 Uhr s.t., MITP seminar room
 Enrico Morgante, Johannes Gutenberg-Universität The relaxion mechanism is a proposed solution to the hierarchy problem, in which the EW scale is set by the classical evolution of a scalar field in the early universe. In this talk, I will review this construction and discuss some recent developments.
06 Nov 2019

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Karin Schönning, Upsala University Many challenges in modern physics manifest themselves in the proton. Despite being known for a century, it is to this day difficult to describe properties like its mass, spin, structure, size and abundance from first principles. One strategy when you have a system you don’t fully understand, is to make a small change to the system and see how it reacts. In the case of the proton, we can replace one of the light quarks with a heavier one and thereby obtain a hyperon. Hyperons have the advantage over protons and neutrons that their spin is traceable through their weak, parity violating and thereby self-analysing decay. In this talk, I will outline how various aspects of hyperons can shed light on two of the puzzles related to the proton: the structure and the abundance. In particular, I will discuss how two recent measurement by the BESIII collaboration exploit the unique properties of hyperons and pave the way for a new generation of hyperon physics experiments.
07 Nov 2019

Seminar über Theorie der kondensierten Materie / TRR146 Seminar

K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Fabian Berressem, Institut für Physik

08 Nov 2019

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Stephan Schlamminger, National Institute of Standards and Technology, Gaithersburg, USA Up to May 20th this year, there was one mass on earth that we knew with absolute precision, i.e., zero uncertainty. This mass was the international prototype of the kilogram. Since May 20th, it is just another mass and thew mass unit is now defined via a fixed value of the Planck constant, h=6.62607015×〖10〗^(-34) "J s" with zero uncertainty. In this presentation, I will explain how the unit of mass can be realized at the kilogram scale via the Kibble balance and the X-ray crystal density method. In the present SI, it is, however, no longer necessary to realize the unit at the cardinal point of 1 kg, it can be realized at any scale. The talk will present some future possibilities of this scale invariant definition of the mass unit. Sondertermin - Bitte um Beachtung!
11 Nov 2019

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
 Hans Christian Lange, Mainz We construct a chiral effective Lagrangian for e.-m. transitions between vector and pseudoscalar mesons (PVgamma). Based on an organization scheme in 1/Nc and the quark masses, we fit up to 12 decays and compare the results of our model with the experimental values given in PDG2018. We will extend our framework to the Dalitz decays PVl+l- and compare the calculated decay rates and transition form factors with recent experimental results.

Seminar about Experimental Particle and Astroparticle Physics (ETAP)

Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Johannes Damp, Institut für Physik

12 Nov 2019

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Warren S. Warren, Department of Physics, Duke University

13 Nov 2019

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Alejandro Kievsky, INFN Pisa The short-range interaction between particles many times shows a strong repulsion that strongly correlated the many-body system. In the particular case of a two-body shallow state, very extended compared to the range of the interaction, the three-body system has universal behavior. There is an infinite number of states geometrically accumulated at E=0. This is the Efimov effect predicted by V. Efimov in 1970 and experimentally verified more than 25 years later. I will discuss how universal behavior emerges in strongly correlated systems as liquid drops or light nuclear systems and how this behavior propagates as the number of particle increases.
14 Nov 2019

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Johannes W. Deiglmayr, Felix-Bloch Institute, Universität Leipzig Exciting an atom or molecule into a high-lying electronic state, a Rydberg state, changes its properties in a drastic, but very well-understood way. While the binding energy of the Rydberg electron decrease with the principal quantum number n as 1/n^2, the orbital radius and transition dipole moments increase as n^2. This results in the electric polarizability increasing as n^7. I will present recent experiments in which we have exploited these scaling laws and exaggerated properties to perform precision measurements of ionization energies with relative accuracies up to 10^11, to characterize precisely static and alternating electric fields, and to reduce the detrimental role of stray fields in applications of Rydberg atoms. In a second part, I’ll discuss our progress towards extracting accurate scattering phase shifts from the spectroscopy of hetero-nuclear long-range Rydberg molecules, which are bound by the interaction of the Rydberg electron with ground-state atoms within its orbit, and how we plan to exploit the exotic properties of long-range Rydberg molecules to create ultracold, strongly correlated plasmas.
18 Nov 2019

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Asia Sobczyk, Valencia
Nuclear effects for neutrino oscillation studies

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Dr. Simon Sels, CERN

Seminar about Experimental Particle and Astroparticle Physics (ETAP)

Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Peter Berta, Institut für Physik

19 Nov 2019

Theorie-Palaver

Institut für Physik14:30 Uhr s.t., MITP seminar room
 Leonardo Vernazza, Nikhef Scattering processes near threshold develop large logarithms, that need to be resummed. In my talk I will focus in particular on electroweak annihilation processes, such as Drell-Yan and Higgs production in gluon fusion, and discuss the underlying factorisation theorems which allow the resummation of such logarithms at next-to-leading power, comparing diagrammatic and effective field theory methods.

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Werner Krauth, Laboratoire de Physique, cole normale suprieure, CNRS Paris

20 Nov 2019

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Christian Weinheimer, Universität Münster Since the discovery of neutrino oscillation we know that neutrinos have non-zero masses, but we do not know the absolute neutrino mass scale, which is as important for cosmology as for particle physics. The direct search for a non-zero neutrino mass from endpoint spectra of weak decays is complementary to the search for neutrinoless double beta-decay and analyses of cosmological data. Today the most stringent direct limits on the neutrino mass originate from investigations of the electron energy spectra of tritium beta-decay. The next generation experiment KATRIN, the Karlsruhe Tritium Neutrino experiment, is improving the sensitivity from the tritium beta decay experiments at Mainz and Troitsk of 2 eV/c^2 by one order of magnitude probing the region relevant for structure formation in the universe. KATRIN uses a strong windowless gaseous molecular tritium source combined with a huge MAC-E-Filter as electron spectrometer. To achieve the sensitivity, KATRIN has been putting many technologies at their limits. The full 70m long setup has been successfully commissioned. From early 2019 on KATRIN is taking high statistics tritium data hunting for the neutrino mass. In this talk an introduction into the necessity to determine the neutrino mass and the status in the field will be given, followed by a detailed presentation of KATRIN and its results from the first KATRIN science run. The new results are already bringing KATRIN into the lead position of the field. In the outlook the perspectives of KATRIN for the coming years and new technologies in the field to potentially improve further the sensitivity on the neutrino mass will be presented.
21 Nov 2019

Seminar über Theorie der kondensierten Materie / TRR146 Seminar

K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
 Dr. Anbumozhi Angayarkan Somasundaram, Weizmann Institute, Rehovot, Israel Phosphatidylcholine (PC) lipids complexed with hyaluronan (HA) have been proposed to form strongly lubricating boundary layers at biosurfaces such as articular cartilage. Depending on the type of PC used, efficient lubrication with friction coefficients down to 10-4 under physiologically high pressures (~100 atm) have been observed. This was attributed to hydration lubrication, acting at the highly hydrated phosphocholine headgroups of the PC lipids, exposed at the liposome surfaces. Such hydration layers can sustain large compressions without water molecules being squeezed out from the gap between sliding surfaces. At the same time, the hydration shells can relax rapidly, ensuring a fluid like response under applied shear. This combination of low shear stresses while sliding under high normal stresses results in very low friction coefficients, an effect termed hydration lubrication. We use the surface force balance (SFB) to examine interactions between polymer layers, in particular how normal interactions and especially frictional interactions, are modified when PC liposomes are added surface in pure water and in aqueous salt solutions, mimicking the presence of macromolecules on the surface of cartilage.
25 Nov 2019

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Farah Afzal, Bonn
Baryon spectroscopy via measurement of polarization observables

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Dr. Sebastian Raeder, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt

Seminar about Experimental Particle and Astroparticle Physics (ETAP)

Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
John Rack-Helleis, Institut für Physik

Masterkolloqium

26 Nov 2019

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Torsten Enßlin, Max Planck Institute for Astrophysics, Garching

27 Nov 2019

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Javier Menéndez, Universitad de Barcelona The rare decay of atomic nuclei known as neutrinoless double-beta Decay is a unique process. Here, a nucleus decays by turning two neutrons into two protons, emitting two electrons without the usual balance of antineutrinos. Therefore, two particles---two electrons---are effectively created. Neutrinoless double-beta decay is the most promising attempt to test lepton number conservation in the laboratory. The observation of neutrinoless double-beta decay would proof that neutrinos are its own antiparticle, can clarify the origin of the prevalence of matter over antimatter in the universe, and determine the absolute neutrino mass. In spite of formidable experimental efforts, neutrinoless double-beta decay remains elusive, with half-live limits set over 10^25 years in some nuclei. The decay rate depends critically on the nuclear structure of the initial and final nuclei. This is encoded in the nuclear matrix element, which is key to anticipate the reach of experiments and to fully extract all physics information from a future measurement. In this PRISMA+ colloquium I will summarize the status of double-beta decay searches, and highlight recent efforts to obtain reliable nuclear matrix elements from first principles.
28 Nov 2019

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Juan Manuel Cornejo-Garcia, Institut für Quantenoptik, Universität Hannover Cosmological observations point to an apparent imbalance of matter and antimatter in our universe, which contrasts with the nearly perfect symmetry arising on the level of single particles. Tests for hypothetical limits to this symmetry rest on high precision comparisons of the fundamental properties of particles and antiparticles - for example, with measurements of the proton and antiproton g-factors in Penning traps. However, these measurements rely on cooling and detections schemes that are highly sensitive on the particle's motional energy [1,2]. In this talk, it will be shown an alternative experimental method which enables a speed up of the particles' preparation and a boost in readout fidelity in the respective experiments [3]. Our method allows for sympathetic cooling of a proton or antiproton to its quantum mechanical ground state and provides readout of their spin state, by means of coupling to a laser cooled 9Be+ ion co-trapped in a double well potential. In addition, an overview of the current experimental setup featuring a cryogenic Penning trap stack for first demonstrations of motional coupling between two 9Be+ ions will be presented. [1] C. Smorra et al., Nature 550, 371-374 (2017) [2] G. Schneider et al., Science 358, 1081-1084 (2017) [3] D. J. Wineland et al., J. Res. NIST 103, 259-328 (1998)
02 Dec 2019

Seminar about Experimental Particle and Astroparticle Physics (ETAP)

Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Florian Thomas, Institut für Physik
Ultra-fast ray-tracing for the Wavelength-Shifting Optical Module

Masterkolloqium

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Daniel Glückman, Karlsruher Institut für Technologie, Institut für Nukleare Entsorgung

03 Dec 2019

Theorie-Palaver

Institut für Physik14:30 Uhr s.t., MITP seminar room
 Matthias Heller, Johannes Gutenberg-Universität The Drell-Yan production of charged lepton pairs is one of the key processes measured at hadron colliders. The QCD corrections to the cross-section are known to order $$\alpha_s^2$$ and electroweak corrections are known to order $$\alpha$$. The next important step for a better theoretical understanding is the complete calculation of the mixed QCD-EW corrections of order $$\alpha \alpha_s$$. In this talk, I report on the first calculation of the virtual two-loop corrections of order $$\alpha \alpha_s$$ to the cross-section. The calculation is carried out analytically using tensor reduction, IBP relations and the method of differential equations. We validate a previous calculation of the subset of mixed QCD-QED corrections and show how the jet and soft functions of that reference can be used to subtract the infrared divergencies of the complete mixed QCD-electroweak virtual corrections. In the talk, I will focus on the calculation of the master integrals, which involve algebraic letters in the differential equation.

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Hendrik Hildebrandt, Faculty of Physics and Astronomy, RU Bochum

05 Dec 2019

Seminar über Theorie der kondensierten Materie / TRR146 Seminar

K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Dr. Jianxiang Shen, Institut für Physik

06 Dec 2019

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für PhysikSonderseminar: 10:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 3. Stock, 03-431
 Akashdeep Ghalayan, Indian Institute of Technology Delhi, India Heusler Alloys have been widely studied due to their potential applications in spintronic devices. Understanding the material's magnetic properties is crucial for deciding its device-based applications. Heusler alloys with high spin polarization (~100 %) and high Curie temperature (~1000 K) are one of the most preferred materials in this regard. The cobalt-based Co2MnAl (CMA) Heusler alloys exhibit more than 50% spin polarization even in the disordered phase with high Curie temperature (Tc ~ 697 K) which is beneficial for device applications. Thin films of CMA with different Co-Mn concentrations have been grown using DC magnetron sputtering at constant growth temperature (Ts ~ 400°C) and film thickness (~ 50 nm) to investigate the effect of Co/Mn concentrations on their electrical transport behavior. X-ray diffraction studies revealed that films possess the A2 disordered phase at room temperature. Magnetic anisotropy, which is vital for magnetic switching device applications, has been investigated using the Longitudinal Magneto-Optic Kerr Effect technique. LMOKE studies revealed the presence of uniaxial magnetic anisotropy in these films. The origin of the uniaxial anisotropy in our films is attributed to obliquely directed material flux onto the substrates during the film-growth. Sonderseminar
09 Dec 2019

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
 Ethan Cline, MIT In 2010 when the CREMA Collaboration released their measurement of the proton radius (Pohl et. al (2010)) from muonic hydrogen spectroscopy: rp=0.84184(67) fm. This was seven standard deviations smaller than the accepted 2010 CODATA value (0.8768(69) fm). This discrepancy lies at the heart of the proton radius puzzle. The MUon-Proton Scattering Experiment (MUSE) was first proposed in 2012 to be the first muon-proton elastic scattering experiment with sufficient precision to address the proton radius puzzle. MUSE has the capacity to simultaneously measure elastic muon-proton, and electron-proton scattering, and switch polarities to measure with opposite charge states. As such, MUSE can directly measure the two-photon effect by comparing charge-states, and compare muon and electron scattering with minimal systematic error. By comparing the two measured scattering cross sections, the experiment will provide more data for the proton radius puzzle and determine if the radius is the same in electron and muon-proton scattering. We will review the motivation for and status of MUSE, which is due to begin production running in 2020. Initial analysis results will be shown from the summer 2019 beam time.

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Katerina Chrysalidis, Universität Mainz / CERN

Seminar about Experimental Particle and Astroparticle Physics (ETAP)

Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Kai Loo, Institut für Physik

10 Dec 2019

Theorie-Palaver

Institut für Physik14:30 Uhr s.t., MITP seminar room
 Guoxing Wang, Peking University The invariant mass distribution of top quark pair production is an important observable whose threshold behavior is sensitive to top-quark mass. In this talk, I will focus on the invariant mass distribution of top-quark pair production in threshold region and soft region. I will first talk about the resummation of Coulomb corrections in threshold limit β → 0. We combine the resummation with fixed-order results and present phenomenologically relevant numeric results. We find that the resummation effect significantly enhances the differential cross section in the threshold region, and makes the theoretical prediction more compatible with experimental data. As for soft limit z → 1, I’ll talk about the calculation of NNLO soft function which is a major bottleneck in pushing up the soft resummation accuracy of top-quark pair production. We show the non-trivial structure of three-parton correlations and the consistent extraction of NNLO soft fragmentation function. At the end, I’ll show the preliminary results of hard function and its application to transverse momentum resummation for top-quark pair production and decay in the future.

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Laura Fabbietti, Physics Department, TU Munich

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für Physik12:00 Uhr s.t., Newton-Raum, Staudingerweg 9, 1. Stock, Raum 122 (Nebengebäude)
 Alexander Tries, Inst. f. Physik tba
11 Dec 2019

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Torben Ferber, DESY Hamburg Belle II in Japan is a flagship experiment at the intensity frontier that started data taking this year after massive upgrades of the accelerator and the detector. In this talk I will report on the performance of the Belle II detector and first rediscoveries with the 2019 dataset. In the second part of the talk I will give an overview about the planned Belle II physics program for the next year with a focus on searches for Dark Sectors and Long-Lived Particles.
12 Dec 2019

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Guillaume Salomon, Max-Planck-Institut für Quantenoptik, Garching Developing new approaches to study quantum many-body systems is of fundamental importance in var­ious felds of physics ranging from high energy and condensed matter physics to quantum information and quantum computation. It also holds promise for a better understanding of materials, such as high-Tc superconductors, and fault-tolerant quantum computing which could strongly impact our modern soci­eties. Ultracold atoms have emerged as versatile and well controlled platforms to study fundamental problems in quantum many-body physics. In particular, spin-resolved quantum gas microscopy enables to probe strongly correlated fermions with a resolution down to the single particle and offers fascinating oppor­tunities for experiments. I will detail here this technique and discuss our recent experimental studies of the interplay between magnetism and doping in the Fermi-Hubbard model, a minimal model for high-Tc superconductivity.

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. Elmers13:30 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Camilo Ulloa, Utrecht University, NL In this talk I will discuss the main concepts of magnon transport through magnetic insulators. I will focus my talk on how to excite and manipulate magnetic degrees of freedom in ferromagnetic materials, and show some of the different ways we can model magnetic insulators, going from quantum mechanics to hydrodynamics.
16 Dec 2019

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
 Varvara Batozskaya, National Centre for Nuclear Research, Warsaw The measurement of the mixing-induced CP-violating phase phi_s in the Bs − B̄s system is one of the key goals of the LHCb experiment. It has been measured at the LHCb collaboration with several decay channels. Thanks to the precise prediction of the phi_s value in the frame of the Standard Model, it represents an excellent probe to search for new physics.

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Dr. Christoph Solbach, Universitätsklinikum Ulm

17 Dec 2019

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Jos Lelieveld, Max Planck Institute for Chemistry, Mainz

Theorie-Palaver

Institut für Physik14:30 Uhr s.t., MITP seminar room
 Fazlollah Hajkarim, Frankfurt University Using the quantum chromodynamics (QCD) equation of state (EoS) from lattice calculations we investigated QCD effects on the first order primordial gravitational waves (PGWs) produced during the inflationary era. We also considered the cases for vanishing and nonvanishing lepton asymmetry where the latter one is constrained by cosmic microwave background experiments. Also, we investigated scenarios that inflation is succeeded by a phase where the energy density of the Universe was dominated by a scalar component with a general equation of state. Then we evaluated the spectrum of primordial gravitational waves induced in the post-inflationary Universe. We showed that if the energy density of the Universe was dominated by some specific fluid 𝜙 before Big Bang Nucleosynthesis (BBN), its equation of state could be constrained by gravitational wave experiments. Moreover, we studied the effect of QCD and electroweak transitions on the induced (or second order) PGW from scalar perturbations which is different from the first order PGW spectrum. Finally, I briefly discuss the production of dark matter (DM) in an early matter era dominated by a heavy long lived scalar field.

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für Physik12:00 Uhr s.t., Newton-Raum, Staudingerweg 9, 1. Stock, Raum 122 (Nebengebäude)
Mariia Filianina, Inst. f. Physik

18 Dec 2019

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Felix Kahlhoefer, RWTH Aachen Over many years the experimental programme to search for dark matter has been guided by the so-called freeze-out paradigm, which assumes that interactions between the dark matter and Standard Model particles are comparable in strength to weak interactions. The non-observation of any dark matter signal has challenged this idea and led to a shift of focus towards dark matter models with even weaker interactions. At first sight, the chance of discovering such particles appears very low, but there are a number of exciting cases where potentially observable signals are predicted in spite of tiny couplings. I will present cosmological and phenomenological aspects of these models and discuss how existing and planned experiments can be used to search for such hidden particles.

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. ElmersSonderseminar: 10:00 Uhr s.t., Gernot-Graeff-Raum, Staudinger Weg 7, 05-431
 Joel Moore, University of California, Berkeley, and Lawrence Berkeley National Laboratory This talk starts by reviewing known examples of how topological materials generate new kinds of electrodynamic couplings and effects. Three-dimensional topological insulators realize a particular electromagnetic coupling known as “axion electrodynamics”, and understanding this leads to an improved understanding of magnetoelectricity in all materials. We then turn to how topological Weyl and Dirac semimetals can show unique electromagnetic responses; we argue that in linear response the main observable effect solves an old problem via the orbital moment of Bloch electrons, and how in nonlinear optics there should be a new quantized effect, which may have been seen experimentally. This nonlinear effect has a natural quantum e^3/h^2 and appears in chiral Weyl semimetals over a finite range of frequencies. We discuss interaction and disorder corrections to nonlinear responses in closing. Sonderseminar TOPDYN

Theory of Condensed Matter: Hard Condensed Matter

Institut für Physik, SPICE10:00 Uhr s.t., Room 05-431 (Gernot-Gräff-Raum)
 Joel Moore, University of California, Berkeley, and Lawrence Berkeley National Laboratory This talk starts by reviewing known examples of how topological materials generate new kinds of electrodynamic couplings and effects. Three-dimensional topological insulators realize a particular electromagnetic coupling known as “axion electrodynamics”, and understanding this leads to an improved understanding of magnetoelectricity in all materials. We then turn to how topological Weyl and Dirac semimetals can show unique electromagnetic responses; we argue that in linear response the main observable effect solves an old problem via the orbital moment of Bloch electrons, and how in nonlinear optics there should be a new quantized effect, which may have been seen experimentally. This nonlinear effect has a natural quantum e^3/h^2 and appears in chiral Weyl semimetals over a finite range of frequencies. We discuss interaction and disorder corrections to nonlinear responses in closing. Work with F. de Juan, A. Grushin, T. Morimoto, D. Parker, J. Orenstein, C. Felser, T. Torchinsky, and others.
19 Dec 2019

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Prof. Dr. Sile Nic Chormaic, OIST Graduate University, Okinawa, Japan Ultrathin optical fibres, with diameters on the order of the propagating light wavelength, have already proven their versatility across a variety of different areas, such as sensing, particle manipulation, cold atom physics, and as optical couplers. The intense evanescent field at the fibre waist is one of the main advantages offered by these systems as it allows us to achieve ultrahigh light intensities that may otherwise not be attainable in a standard laboratory. In this talk, I will present work conducted at OIST with particular focus on our work on optical nanofibre-mediated multiphoton processes for the generation of highly excited Rydberg atoms and for exploring some other effects, such as quadrupole transitions and stimulated emission from Rb atoms. Overall, the versatility of these fibres for many different experimental platforms particularly if one goes beyond the basic, single mode fibre design will be promoted.

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. Elmers13:30 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Prof. Dennis Meier, Norwegian University of Science and Technology, Trondheim Domain walls naturally arise whenever a symmetry is spontaneously broken. They interconnect regions with different realizations of the broken symmetry, promoting structure formation from cosmological length scales to the atomic level. In my talk, I will present domain walls with unique functionalities which emerge in spin-spiral multiferroics and chiral magnets and which hold great promise for nanoelectronics and spintronics applications. In particular, I will discuss that a wide variety of new domain walls occurs in the presence of spatially modulated domain states. In contrast to domain walls in conventional ferroics, such domain walls exhibit a well-defined inner structure, which — analogous to cholesteric liquid crystals — consists of topological disclination and dislocation defects. Similar to the magnetic skyrmions, the domain walls can carry a finite topological charge, permitting an efficient coupling to spin currents and contributions to a topological Hall effect. Our studies establish domain walls in chiral magnets as functional nano-objects with non-trivial topology, opening the door to innovative device concepts in information and communication nanotechnology.
06 Jan 2020

Seminar about Experimental Particle and Astroparticle Physics (ETAP)

Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Niklas Schmitt, University of Mainz
Suche nach dunkler Energie in Monojet-Ereignissen bei 13TeV mithilfe des ATLAS-Detektors am LHC

Bachelorkolloqium

07 Jan 2020

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Christian Enss , Kirchhoff Institute for Physics, Heidelberg

08 Jan 2020

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Cristina Lazzeroni, University Birmingham, UK The decay K+→π+vv ̅, with a very precisely predicted branching ratio of less than 10-10, is one of the best candidates to reveal indirect effects of new physics at the highest mass scales. The NA62 experiment at the CERN SPS is designed to measure the branching ratio of the K+→π+vv ̅ with a decay-in-flight technique. NA62 took data so far in 2016-2018. Statistics collected in 2016 allowed NA62 to reach the Standard Model sensitivity for K+→π+vv ̅, entering the domain of 10-10 single event sensitivity and showing the proof of principle of the experiment. Thanks to the statistics collected in 2017, NA62 surpasses the present best sensitivity. The preliminary result from the 2017 data set is presented. The general status of the experiment, including other recent measurements, are presented. Plans for the next data taking and for a longer term future are also discussed.
09 Jan 2020

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Jun.-Prof. Dr. Jamir Marino, Institut für Physik, Universität Mainz The talk will discuss instances of dynamical phases of interacting quantum many body models where coherent and dissipative dynamics occur on equal footing, shaping novel non-equilibrium phase diagrams. The first part of the talk will discuss long-range interacting quantum simulators where an external periodically driven field can stabilise phases without equilibrium counterpart against instabilities triggered by many body quantum fluctuations. In the second part, I will present an instance of ‘cold' time crystal occurring in open quantum systems, where neither MBL or pre-thermalisation are required to stabilise a strongly interacting non-equilibrium steady state. Time permitting, I will advertise some novel results on a purely dissipative analogue of long-range interacting quantum simulators, which can be implemented in quantum optics or solid state platforms.
13 Jan 2020

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Dr. Marine Vandebrouck, CEA Saclay

Theoriekolloquium

Die Dozierenden der Theoretischen PhysikSonderseminar: 14:00 Uhr s.t., Medienraum, Staudinger Weg 7, 03-431
 Prof. James Freericks, Georgetown University, USA Quantum mechanics was created with the matrix mechanics of Heisenberg, Born, and Jordan. Schroedingers wave mechanics shortly followed and allowed for simpler and more powerful calculations. Both Pauli and Dirac introduced a formulation of quantum mechanics based on operators and commutation relations, but it was never fully developed in the 1920s. Instead, Schroedinger formulated the operator approach with his factorization method, which later was adopted by the high-energy community as supersymmetric quantum mechanics. In this talk, I will explain how one can formulate all of quantum mechanics algebraically by a proper use of the translation operator on top of Schroedingers factorization method. I will give examples of how one can compute spherical harmonics algebraically, how one can find harmonic oscillator wavefunctions, and will even describe an operator-based derivation of the wavefunctions of Hydrogen. I will end with a proposal for a novel way to teach quantum mechanics, focusing first on conceptual ideas related to superposition, projective measurements, and entanglement. Then developing more conventional topics like spin, harmonic oscillator, angular momentum, interacting spin models, central potentials, particles in a box and so on. This is the subject of a book in progress entitled Quantum Mechanics without Calculus. Sonderseminar Sondertermin/-raum Montag, 14:15 h im Medienraum, Staudinger Weg 7, 03-431

Seminar about Experimental Particle and Astroparticle Physics (ETAP)

Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Julian Fischer, Institut für Physik

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für PhysikSonderseminar: 10:00 Uhr s.t., MEDIEN-Raum, Staudingerweg 7, 3. Stock, Raum 03-431
 Abhishek Erram , Indian Institute of Technology Kharagpur In this work, we have made a polycrystalline sample of Dy2BaNiO5 by a standard solid-state reaction route. The formation of the compound was ascertained by x-ray powder diffraction pattern. The dc χ measurements were carried out in the temperature interval 5–300 K in the presence of magnetic fields of 100 Oe and 5 kOe for zero-field-cooled (zfc) and field-cooled (fc) conditions using (SQUID) and isothermal magnetization (M) behavior was studied at a certain selected low temperature. Then, Thin film of Dy2BaNiO5 certain thickness were deposited on Mgo , Al203 ,STO and LAO substrate by Pulsed Layer Deposition method these films were annealed at temperature 650 oC. Some of the samples were Characterized by X-ray diffraction (XRD). Magnetic behavior was also studied. Results show that of formation of thin film. Signs of magnetic behavior was also evident. Sonderseminar
15 Jan 2020

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Christian Fischer, Universität Gießen In this talk I will give an overview on recent results on the spectrum and properties of conventional baryons and 'exotic' tetraquarks as obtained in the framework of Dyson-Schwinger and Bethe-Salpeter equations. I will discuss the spectrum of light baryons with focus on the comparison with quark model expectations, the impact of dynamical mass generation and the importance of relativistic components in the wave functions of baryons. I will also discuss extensions to SU(3). For four-quark systems I will summarize results for light quarks and discuss recent progress on discriminating between tetraquark, molecule or hadro-quarkonium configurations in heavy-light systems.

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik10:30 Uhr s.t., QUANTUM Seminarraum (02-427), Institut für Physik, Staudingerweg 7
 Brian Rost and Lorenzo Del Re , Georgetown, USA The driven dissipative many body problem is one of the longest standing unsolved problems in physics and it has experienced a renewed interest in the last decade. In fact, dissipation has been theoretically proposed as a resource for quantum computation and experimentally has been demonstrated that it can be employed to prepare maximally entangled states. Thus, quantum computers could shed some light on the unsolved problem of driven-dissipative quantum systems but there are many choices for how one engineers the reservoir. An attractive approach is to integrate the bath degrees of freedom out via a master equation. Here we show how accurate this approach is by comparing it to an exact solution in the case of a tight-binding dissipative-driven model of fermions coupled to an external fermionic bath, and how to actually simulate it on a currently available IBM quantum computer. We also address the case of an interacting dissipative-driven finite size system, i.e. a three-site Hubbard model with on-site interaction driven by an external field and coupled to a bath. Here, we obtain many of the qualitative features already displayed in the thermodynamic limit. The biggest challenge in implementing these ideas on current quantum computers lies with the need for partial resetting of qubits. We discuss strategies to implement on commercially available hardware and what might be possible with academic machines (such as those available at Mainz). Sondertermin und -ort
16 Jan 2020

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. Elmers11:30 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Dr. Dongwook Go, Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich Electrical control of magnetism is a central theme in the field of spin-orbitronics. Current scheme relies on electrical generation of the spin current/density by utilizing the spin-orbit coupling (SOC) instead of using an extra ferromagnet (FM) as a spin polarizer. For example, in a bilayer structure consisting of a FM layer and a nonmagnet (NM) layer, spin current and density can be induced by the spin Hall effect in the NM and Rashba-Edelstein effect at the NM/FM interface, respectively. However, there has been a missing piece in spin-orbitronics so far: electrons carry angular momentum in the orbital wave function as well as in the spin. In this seminar, I demonstrate that the orbital degree of freedom exhibits rich dynamical phenomena, which is in contrast to a common expectation that the orbital is quenched in solids. In the first part, I explain how to electrically generate the orbital angular momentum. Here, I introduce concepts of the orbital Rashba-Edelstein effect [1] and the orbital Hall effect [2], which are orbital analogs of the Rashba effect and the spin Hall effect, respectively. These are not only parental effects for their spin analogs, such that the spin phenomena follow the orbital phenomena by the SOC, but also present even in the absence of the SOC. In the second part, I focus on the consequence of the injection of the orbital angular momentum into the FM. As the spin injection gives rise to the spin torque (ST), the orbital injection results in torque on the magnetic moment, which we call orbital torque (OT) [3]. In the mechanism of the OT, it is not necessary to prepare the spin current or density beforehand as in the conventional mechanisms such as the spin Hall effect and Rashba-Edelstein effect. Since both OT and ST contribute to magnetic dynamics, it opens a route to enhancing the torque efficiency in spin-orbitronic devices. Interestingly, we notice that the sign of the torque efficiency in the NM/FM bilayer can be opposite to the sign of the spin Hall effect in the NM if the sign of the OT differs from that of the ST. As a prototypical example, I compare Fe/W(110) and Ni/W(110) bilayers from first principles calculation and discuss qualitatively distinct features of the OT for the experimental detection [4]. As the study on the orbital dynamics has started very recently, I briefly discuss future directions for consistent understanding of entangled dynamics of the spin and orbital degrees of freedom in solids.

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Shane P. Kelly, Theoretical Division, LANL, Los Alamos, USA In recent years, many experimental platforms have succeeded in producing quantumsystems that, on relevant time scales, are completely isolated from an environment. This opens the possibility of observing equilibrium states that are not described by standard thermal ensembles and long time dynamics that indefinitely maintain memory of initial states. In this talk, I discuss two mechanisms for this to occur: many body localization (MBL) and a novel mechanism which occurs in the semi-classical limit of a large spin. In the first part of my talk, I will discuss the phenomenon of MBL in a disordered spin chain and its effects when coupled to a small environment. We model this small environment as a clean spin chain and find that, under sufficient coupling and disorder, the dirty chain can induce an MBL effect in the clean chain. In the second part of my talk, I will discuss the dynamics of a large spin evolving with a non-linear hamiltonian. Using semi-classical techniques, we identify when the spin does and does not thermalize. In doing so, we find a novel mechanism for the breakdown of thermalization based on the slow dynamics of an unstable fixed point.
20 Jan 2020

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Christoph Matejcek, Mainz
Low-energy beam transport system for MESA

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Dr. Zsolt Baranyi, Universität BRACCO

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik16:15 Uhr s.t., QUANTUM Seminarraum (02-427), Institut für Physik, Staudingerweg 7
 Dr. Guanghua Du, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China When heavy ion beam with energy from MeV to GeV is incident on the target material, the target material distributed along the ion trajectory will be excited or ionized, which will cause lattice damage, polymer chain break or cross-linking in the material and then result in nanoscale latent track, cluster damage and single event effect. The high energy microbeam facility of Lanzhou National Laboratory of Heavy Ion Accelerator is the highest energy microbeam system in the world which uses triplet-quadrupole magnets to produce micron sized high energy ion beams of up to several GeVs. This talk first introduces the accelerator complex and nuclear physics activity at Lanzhou National Lab, and then focuses on the interdisciplinary application of the high energy microbeam facility, including single event effect studies, single ion hitting, nanomaterials, and biomedical studies. Sondertermin und -ort
21 Jan 2020

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Victorino Franco, Condensed Matter Physics, Universidad de Sevilla

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für Physik12:00 Uhr s.t., Newton-Raum, Staudingerweg 9, 1. Stock, Raum 122 (Nebengebäude)
Olga Lozhkina, Inst. f. Physik

Theory of Condensed Matter: Hard Condensed Matter

Institut für Physik, SPICE14:00 Uhr s.t., Galilei Room, 01-128 (Staudinger Weg 9)
 Souvik Paul, Christian-Albrechts-Universität zu Kiel Magnetic skyrmions, localized spin structure with topological protection, have become a research hotspot as they show promise for future memory and logic devices. The key challenges for applications are to achieve small bits and stability of those skyrmionic bits. Research shows that transition-metal interfaces (TMI) and multilayers are a very promising class of systems to realize nanometer-sized and stable magnetic skyrmions. Therefore, a lot of effort has been put to tailor the properties of these systems for application. In this direction, using first-principles methods, we have proposed ultrathin films, Fe/Rh and Rh/Fe bilayers on Re(0001) substrate, which show various spin structures at the interface including isolated skyrmions, depending on the stacking order of Fe/Rh and Rh/Fe bilayers. This study would encourage the experimentalist to check our predictions and would generate more investigations on other bilayers on Re(0001). The other topic I would focus on is the effect of higher-order exchange interactions (HOI) on the stability of skyrmions. HOI are shown to stabilize magnetic ground states in transition-metal ultrathin films, however, their role on the stability of metastable skyrmions has note been investigated yet. We showed that the HOI increase the stability of skyrmions by a large amount at TMI. This study opens up a route to tune skyrmions stability and lifetime in ultrathin films. [1] Nat. Nanotechnol. 8, 899–911 (2013) [2] Sci. Rep. 4, 6784 (2014) [3] Nat. Commun. 5, 4652 (2014) [4] arXiv:1912.03465 [5] Nat. Phys. 7, 713 (2011) [6] Phys. Rev. Lett. 120, 207201 (2018) [7] Phys. Rev. Lett. 120, 207202 (2018) [8] arXiv:1912.03474
22 Jan 2020

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Assumpta Parreno, Universitad de Barcelona A central goal of Nuclear Physics is to obtain a first-principles description of the properties and interactions of nuclei from the underlying theory of the strong interaction, Quantum Chromodynamics (QCD). Being the theory that governs the interactions between the basic building blocks of matter, quarks and gluons, it is also responsible for confining those primary pieces into hadronic states, binding neutrons and protons through the nuclear force to give the different elements in the periodic table. Nevertheless, due to the large complexity of the quark-gluon dynamics, one cannot obtain analytical solutions of QCD in the energy regime relevant to nuclear physics. In order to address this problem, numerical solutions of QCD can be obtained in a finite volume through its formulation in a Euclidean discretized space-time. I will present the results of our study in the two-baryon sector for different values of the light quark masses, as well as for the very light A=3,4 nuclei.
23 Jan 2020

Seminar über Quanten-, Atom- und Neutronenphysik (QUANTUM)

Institut für Physik14:00 Uhr s.t., Lorentz-Raum (05-127), Staudingerweg 7
 Dr. Maria Chekhova, Institut für Optik, Information und Photonik, Universität Erlangen Spontaneous parametric down-conversion is the workhorse of quantum optics. This process is used to generate entangled photon pairs and heralded single photons. When strongly pumped, spontaneous parametric down-conversion generates so many photon pairs that they overlap and form radiation with almost laser brightness. Despite being bright, this radiation manifests nonclassical effects: quadrature squeezing, photon-number correlations, and macroscopic entanglement. It has no coherent component and can be considered as amplified vacuum noise; it is therefore often called bright squeezed vacuum. In addition, strong photon-number fluctuations of bright squeezed vacuum make it extremely efficient for pumping multiphoton effects. My talk will cover this and other applications of strongly pumped parametric down-conversion. In addition, I will talk about the other extreme case of this process. Namely, if photon pairs are generated in a very thin nonlinear layer, the process does not require phase matching – in other words, the momentum of the pump photon is not conserved by the daughter photons. To demonstrate this, I will show the results of generating photon pairs from a 300 nm layer. This nanoscale generation of entangled photons offers unique radiative characteristics: the frequency-angular spectrum is extremely broad and as such it promises subwavelength and subcycle two-photon correlation widths in position and time, respectively. Additionally, it gives an insight into the subwavelength resonances for vacuum fluctuations.

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Stéphane Mangin, Institut Jean Lamour, UMR CNRS 7198, Université de Lorraine, Nancy, France During the last decade all-optical ultrafast magnetization switching in magnetic material thin film without the assistance of an applied external magnetic field has been explored [1,2]. It has been shown that femto-second light pulses can induce magnetization reversal in a large variety of magnetic materials [3,4]. However, so far, only certain particular ferrimagnetic thin films exhibit magnetization switching via a single femto-second optical pulse. We will present the single-pulse switching of various magnetic material (ferrimagnetic, ferromagnetic) within a magnetic spin-valve structure and further show that the four possible magnetic configurations of the spin valve can be accessed using a sequence of single femto-second light pulses. Our experimental study reveals that the magnetization states are determined by spin-polarized currents generated by the light pulse interactions with the GdFeCo layer [5]. A detail study showing how spin-polarized currents are generated and how they interact with magnetic layers (Ferromagnetic or Ferrimagnetic) to lead to magnetization switching will be presented.
24 Jan 2020

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für Physik13:30 Uhr s.t., MEDIEN-Raum, Staudingerweg 7, 3. Stock, Raum 03-431
 Mona Minakshee Manjaree Bhukta , National Institute of science education and research, Bhubaneswar, India 1.Thermal diffusion of nπ Skyrmion and Skyrmion bags Skyrmionics have recently emerged as active field of research because of their potential applications in high density data storage technology and logic gate computing. Magnetic skyrmions correspond to localized whirling spin configurations, which are characterized by a topological charger (Q). Recent atomistic simulations and experimental finding ensure the diffusive behaviour of skyrmion at finite temperatures in ultrathin model, which open up the possibility of application thermal induced skyrmion dynamics in probabilistic computing. In this work we studied the thermal diffusion of nπ skyrmion up to n= 5 and N skyrmion bag (N (= 1-6) skyrmion surrounded by a bigger skyrmion with opposite chirality) using atomistic spin simulation on Pt_{0.95}/Ir_{0.05} on Pd (111) bilayer by statistically averaging out 100s of these spin texture. Further the SkHE of all these structures has been calculated using both simulation and analytics. 2.Frustrated Skyrmionic States in synthetic Antiferromagnet The spherical topology of a skyrmion leads to an extra force, that acts on moving skyrmion, pointing perpendicular to its velocity. This deviates the path of the skyrmion towards the edge of the nanotrack and this phenomenon is referred as the Skyrmion Hall effect (SkHE). In an antiferromagnetically exchange-coupled bi-layer nanotrack, this SkHE could be suppressed without affecting the topological protection of the skyrmion. Recently it is shown that skyrmion in frustrated ferromagnets have more helicity and vorticity degrees of freedom in compared with the skyrmion stabilized by Dzyaloshinskii-Moriya Interaction (DMI). In this work, we attempted to model a system using micromagnetic simulation to induce frustration by taking RKKY interaction as perturbation in a Synthetic antiferromagnet (SAF). The frustration in the system could be due to the equivocation of DMI between two antiferromagnetically coupled layer. We not only found the existence of Q = 0 skyrmion, but also able to stabilize the skyrmion and antiskyrmion in the same layer. Later we deposited Ta/(Pt/Co)_2/Ir(x)/Co/Pt (x= 0.5 and 1.0 nm) on Silicon substrate using DC magnetron sputtering to optimize the SAF nature of the thin films and to observe the domain images using Kerr Microscope.
27 Jan 2020

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Alexey Tyukin, Mainz
Momentum transfer reconstruction for the P2 Experiment

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Dr. Christian Smorra, Institut für Physik, JGU Mainz

Seminar about Experimental Particle and Astroparticle Physics (ETAP)

Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Michael Wurm, Institut für Physik

28 Jan 2020

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Professor Manfred Popp, Karlsruher Institut für Technologie

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für Physik12:00 Uhr s.t., Newton-Raum, Staudingerweg 9, 1. Stock, Raum 122 (Nebengebäude)
Stanislav Bodnar, Inst. f. Physik

Theorie-Palaver

Institut für Physik14:30 Uhr s.t., MITP Seminar Room
 Fabian Lange, RWTH Aachen The Gradient-Flow formalism was primarily introduced for simulations of Quantum Chromodynamics (QCD) on the lattice and has now found widespread use in this field. In addition, it offers the potential for cross-fertilization between perturbative and lattice calculations. In my talk I will introduce the Gradient-Flow formalism and outline the perturbative approach. Afterwards, I will present two examples of its applications. First, I will show how it could be used to extract the strong coupling constant from lattice simulations. As second application, I will illustrate how it helps to define the energy-momentum tensor of QCD on the lattice.
29 Jan 2020

PRISMA Colloquium

Institut für Physik13:00 Uhr s.t., Lorentz-Raum 05-127, Staudingerweg 7
 Jonathan Butterworth, UCL London Particle-level, differential measurements made in fiducial regions of phase-space at colliders have a high degree of model-independence and can therefore be compared in a very generic way not only to precision Standard Model predictions, but to beyond the Standar Model physics implemented in Monte Carlo generators. This allows a wider array of final states to be considered than is typically the case, as well as a wider array of specific models, and optimises the long-term impact of precision LHC data. I present a method of exploiting this, with examples.
30 Jan 2020

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MAINZ-Seminarraum, Staudinger Weg 9, 03-122
 Prof. Matthias Wuttig, RWTH Aachen University of Technology, Germany It has been a long-time dream of mankind to design materials with tailored properties. In recent years, the focus of our work has been the design of phase change materials for applications in data storage. In this application, a remarkable property portfolio of phase change materials (PCMs) is employed, which includes the ability to rapidly switch between the amorphous and crystalline state. Surprisingly, in PCMs both states differ significantly in their properties. This material combination makes them very attractive for data storage applications in rewriteable optical data storage, where the pronounced difference of optical properties between the amorphous and crystalline state is employed. This unconventional class of materials is also the basis of a storage concept to replace flash memory. This talk will discuss the unique material properties, which characterize phase change materials. In particular, it will be shown that only a well-defined group of materials utilizes a unique bonding mechanism (‘Bond No. 6’), which can explain many of the characteristic features of crystalline phase change materials. Different pieces of evidence for the existence of this novel bonding mechanism, which we have coined metavalent bonding, will be presented. In particular, we will present a novel map, which separates the known strong bonding mechanisms of metallic, ionic and covalent bonding, which provides further evidence that metavalent bonding is a novel and fundamental bonding mechanism. This insight is subsequently employed to design phase change materials as well as thermoelectric materials. Yet, the discoveries presented here also force us to revisit the concept of chemical bonds and bring back a history of vivid scientific disputes about ‘the nature of the chemical bond’.
31 Jan 2020

Seminar über Theorie der kondensierten Materie / TRR146 Seminar

K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. VirnauSonderseminar: 10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Philipp Arras, MPI Astrophysics, Garching
Information field theory and applications in calibration and imaging algorithms

Sonderseminar

03 Feb 2020

Institut für Kernchemie16:00 Uhr s.t., Seminarraum Kernchemie
Prof. Dr. Bernd Krause, Universität Rostock
Thema folgt

Institut für Kernphysik14:00 Uhr s.t., HS Kernphysik, Becherweg 45
Oliver Noll, Mainz

Seminar about Experimental Particle and Astroparticle Physics (ETAP)

Institut für Physik12:30 Uhr s.t., Staudingerweg 7, Minkowskiraum
Christopher Hils, Insitut für Physik

04 Feb 2020

Physikalisches Kolloquium

Institut für Kernphysik, Remote Seminar16:00 Uhr s.t., HS KPH
Dr. Friederike Otto, ECI, University of Oxford
COLLOQUIUM CANCELLED! Angry Weather How Climate Change is affecting extreme Weather around the World

COLLOQUIUM CANCELLED!

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für Physik12:00 Uhr s.t., Newton-Raum, Staudingerweg 9, 1. Stock, Raum 122 (Nebengebäude)
Amrit R. Pokharel, Inst. f. Physik

Theorie-Palaver

Institut für Physik14:30 Uhr s.t., MITP seminar room
 Avirup Ghosh, Harish Chandra Research Institute The existence of Dark Matter (DM) as one of the major component of our universe is inevitable today. Though there are several evidences of DM, all of them are gravitational in nature. The particle nature of DM is yet unknown. The most popular theory of particle DM is Weakly Interacting Massive Particles(WIMP) which though very interesting from the point of view of naturalness, is not yet tested in experiments. On the other hand, Feebly Interacting Massive Particles (FIMP) as an alternative scenario is gaining attention in recent times which due to their feeble interaction can not be observed in current generation of experiments. I shall discuss in my talk how in some FIMP scenarios the tiny coupling of FIMP DM give rise to interesting signals.
06 Feb 2020

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MAINZ Seminarraum, Staudinger Weg 9, 3. Stock, 03-122
 Markus Garst, KIT Karlsruhe, Germany The weak Dzyaloshinskii-Moriya interaction (DMI) in chiral magnets stabilizes spatially modulated magnetic textures like helices and skyrmion crystals. In this talk we focus on the dynamical properties of such textures. In the field-polarized phase of chiral magnets, the DMI results in a pronounced non-reciprocity of the magnon spectrum, i.e. the excitation energy is not symmetric with respect to an inversion of the wavevector. In the conical helix phase, the spin waves experience Bragg scattering off the periodic magnetic texture that leads to a backfolding of the magnon spectrum. As a result, the spectrum becomes reciprocal for wavevectors along the helix axes. However, the distribution of spectral weight in the spin structure factor remains non-reciprocal as confirmed by inelastic neutron scattering [1,2]. For wavevector with a finite perpendicular component of the wavevector, dipolar interactions induce a non-reciprocity which was detected by Brillouin light scattering [3]. We also discuss the spin wave spectrum of the skyrmion crystal phase where the non-trivial topology leads to an emergent electrodynamics for magnons. As a result the spectral weight of the spin structure factor is widely distributed at high energies. The spin wave excitations propagating along the skyrmion strings also exhibit a non-reciprocity as confirmed by spin wave spectroscopy [4]. Finally, we discuss the non-linear dynamics of a single skyrmion string [5].

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für PhysikSonderseminar: 15:15 Uhr s.t., MAINZ Seminarraum, Staudinger Weg 9, 3. Stock, 03-122
Kelvin van Hoorn, Technical University of Eindhoven, The Netherlands

Sonderseminar

07 Feb 2020

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für PhysikSonderseminar: 15:00 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 3. Stock, Raum 03-431
 Chi Fang, University of Chinese Academy of Sciences, Beijing, China The application potential of spin-orbit-torques in magnetic random access memory attracts great attention and research interest in spin-orbit coupling in heavy metals like Platinum and Tantalum. Thus the spin relaxation time τ_s, as a crucial parameter to investigate spin relaxation mechanism in the heavy metals, requires accurate and effective estimation. A traditional three-terminal method is also widely utilized to estimating τ_s of semiconductors and light metals. Its reliability, however, has recently been challenged by some experiments in which tunneling anisotropic magnetoresistance (MR) or spin blockage MR rather than the MR induced by spin injection and subsequent Hanle effect is more appropriate to explain the data. In this talk, I will introduce the spin-injection-induced magnetoresistance of which the magnitude is comparable with other MR phenomena originating from the tunnel barrier is observable at room temperature as well as low temperatures in the second harmonic signals. Three-terminal and second harmonic method are combined in our measurement in Pt and Ta systems. Furthermore, we could estimate τ_s of heavy metals through fitting the signal with Lorentz function. This experimental approach make it possible to directly acquire τ_s of heavy metals with electrical method. Sonderseminar
19 Feb 2020

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für PhysikSonderseminar: 14:30 Uhr s.t., MEDIEN-Raum, Staudinger Weg 7, 3. Stock, Raum 03-431
 Dr. Kunie Ishioka, National Institute for Materials Science, Tsukuba, Japan Mittwoch, den 19. Februar 2020 um 14:30 im MEDIEN-Raum, Staudinger Weg 7, 03-431 Ultrafast Carrier and Phonon Dynamics of Hybrid Lead Halide Perovskite Kunie Ishioka National Institute for Materials Science, Tsukuba, Japan Inorganic-organic hybrid lead halide perovskites, consisting of the soft lead halide octahedral framework and the organic molecular cations, are among the key materials for the next generation photovoltaics. In the first half of my talk I present on the charge separation dynamics at the interfaces of methylammonium lead iodide MAPbI3 with three different hole transport materials (HTMs) [1]. Here, the differential transmission signals revealed the hole injection from the perovskite to organic HTMs to occur on the time scale of 1 ps, whereas that to inorganic NiOx on an order of magnitude longer timescale. The anti-correlation with the fill factor of the solar cells suggests that the interfacial quality was responsible. In the second half I present our recent results on the coherent phonons of MAPbI3 [2]. We observe periodic modulations in the transient transmissivity due to the photoinduced libration and torsion of the methylammonium cations and the deformation of the PbI6 octahedral framework. The frequencies of the cation torsion and the octahedral deformations exhibited downchirps, in agreement with theoretically predicted strong anharmonicities of their vibrational potentials. Sonderseminar Sondertermin
27 Feb 2020

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. Elmers14:15 Uhr s.t., MAINZ Seminarraum, Staudinger Weg 9, 3. Stock, 03-122
Shefali Vaidya, IRCELYON, Lyon, France

05 Mar 2020

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. Elmers14:15 Uhr s.t., MAINZ Seminarraum, Staudinger Weg 9, 3. Stock, 03-122
Thomas Allison, Stony Brook University, NY, USA

Seminar über Theorie der kondensierten Materie / TRR146 Seminar

K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Fabian Kössel, Institut für Physik
Emerging patterns from the collective dynamics of microswimmers in an external field

Trial PhD defense talk

10 Mar 2020

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., Galilei seminar room (Staudinger Weg 9, room 01-128)
Mehrdad Elyasi, Tohoku University, Sendai, Japan

12 Mar 2020

SFB/TR49/SFB TRR 173 Spin+X-Kolloquium/TopDyn - Seminar experimentelle Physik der kondensierten Materie

SFB/TR49 - Prof. Dr. Elmers14:00 Uhr s.t., MAINZ seminar room (Staudinger Weg 9, 3rd floor, room 03-122)
Dr. Aga Shahee, Seoul University

Seminar über Theorie der kondensierten Materie / TRR146 Seminar

K. Binder/ A. Nikoubashman / F. Schmid / G. Settanni / T. Speck / M. Sulpizi / P. Virnau10:30 Uhr s.t., Newtonraum, 01-122, Staudingerweg 9
Jan Rothörl, Institut fuer Physik
Creating 3D structures of diploid cells from Hi-C data using a Molecular Dynamics approach

Master Colloquium

13 Mar 2020

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für PhysikSonderseminar: 11:00 Uhr s.t., MEDIEN-Raum, Staudingerweg 7, 3. Stock, Raum 431
 Jonas Knobel, Universität Würzburg New directions in spintronics heading towards devices based on antiferromagnetic materials require a fundamental understanding of the underlying physics. CuMnSb grown by molecular beam epitaxy (MBE) on GaSb substrates can provide a model system of a thin film antiferromagnet. I will report on the growth of virtually unstrained pseudomorphic single crystals showing clear antiferromagnetic behavior. The ordering temperature of CuMnSb between 50K and 62K lies well within the reach of standard cryostats. This allows to diff erentiate thermal from magnetic properties in transport devices. I will first discuss the epitaxial growth of a GaSb buff er layer needed for a sharp interface. Subsequent CuMnSb growth is highly dependent on the flux ratios of the respective elements. I will explain their influence on crystal properties and how reflection high-energy electron di ffraction (RHEED) is used to control the growth process. Sonderseminar

Seminar Festkörper- und Grenzflächenphysik KOMET - experimentell

Institut für PhysikSonderseminar: 14:00 Uhr s.t., MEDIEN-Raum, Staudingerweg 7, 3. Stock, Raum 431
 Kanji Furuta, Department of Materials Science and Engineering, Nagoya University, Japan. MAX phase compounds have recently attracted much attention due to their possible application to the production of a new class of two-dimensional systems called MXenes [1]. Mo4Ce4Al7C3 is affiliated with the MAX phase and in a family of RE-based nanolaminates with a chemical formula of Mo4RE4Al7C3. From magnetization measurements, x-ray absorption near-edge structure (XANES), and x-ray magnetic circular dichroism (XMCD), a ferromagnetism below a Curie temperature of TC ~ 10.5 K and a mixed-valence states of the Ce 4f electrons have been reported [2]. To understand the origin of electronic/magnetic properties of Mo4Ce4Al7C3, we have performed angle-resolved photoemission spectroscopy (ARPES) on Mo4Ce4Al7C3 single-crystals. As a result, we have succeeded to obtain the electronic band structure as well as Fermi surface of this system. From the comparison between Ce 4d-4f on and off resonant ARPES, strong Ce 4f character at the electron pocket around the G point has been elucidated. Furthermore, we have found a clear increase of the Ce 4f spectral weight below TC. The results suggest that itinerant Ce 4f electrons may play an important role in the magnetic properties of Mo4Ce4Al7C3. REFERENCES [1] M. Barsoum, MAX phases (Wiley, Weinheim, 2013). [2] Q. Tao et al., Phys. Rev. Mat. 2, 114401 (2018). Sonderseminar