Archived Events

You can find slides of some of the archived seminars by clicking "More.." at the archived entry or all available slides assembled in the internal section.

10.11.2023, 10:00 am

Dr. Claudia Artiaco - KTH Stockholm
i-RTG Lecture in Röntgen-HS

Title: Hands-on the local-information time evolution approach

Abstract:
In this lecture, I will provide practical insights into the numerical implementation of the local-information time evolution (LITE) algorithm. The lecture is tailored for those interested in applying LITE in their research or seeking a better understanding of this approach. I will discuss the construction of the information lattice, computation of local information and information currents, calculation of higher-level subsystem density matrices using the projected Petz recovery map, minimization of information at a specific scale while keeping lower-level subsystem density matrices and information currents fixed, and conducting simulations for infinitely extended systems from asymptotically time-invariant initial states. I will also describe the numerical parameters used in the LITE algorithm and provide pseudo codes illustrating the algorithm's workflow. All the content covered can be found in references [1] and [2].

References:

[1] T. Klein-Kvorning, L. Herviou, and J. H. Bardarson, Time-evolution of local information: Thermalization dynamics of local observables, SciPost Phys. 13, 080 (2022).

[2] C. Artiaco*, C. Fleckenstein*, D. Aceituno, T. Klein-Kvorning, and J. H. Bardarson, Efficient Large-Scale Many-Body Quantum Dynamics via Local-Information Time Evolution, arXiv:2310:06036.

* These alphabetically ordered authors contributed equally.

28.07.2023, 10:00 am

Dr. Benjamin Lenz - Sorbonne Université, Paris
i-RTG Lecture in Röntgen-HS

Title: Some aspects of strongly correlated materials as viewed through the lens of cluster dynamical mean-field theory

Abstract:
In this lecture, we will look at the theoretical description of strongly correlated materials using one of the state-of-the art techniques to calculate their low-energy electronic properties, so-called cluster dynamical mean-field theory (C-DMFT). First, I will recall certain basic notions of theoretical solid state physics needed to interpret experimental probes such as angle-resolved photoemission spectroscopy (ARPES). A particular focus will be set on strongly correlated materials which necessitate a many-body description of the electronic part of the solid to understand its electronic and magnetic properties at low temperature. Taking a high-temperature superconducting cuprate material as test case, we will discover how a seemingly simple effective model for strongly correlated materials requires rather sophisticated techniques like C-DMFT to obtain good agreement with experiments.

20.07.2023, 10:00 am

Dr. Martin Svec - Institute of Physics of the Czech Academy of Sciences
i-RTG Lecture in Röntgen-HS

Title: TBA

Abstract:
TBA

17.03.2023, 10:00 am

Eleonora Barbano - Fakultät für Physik und Astronomie, Universität Würzburg
i-RTG Lecture in Röntgen-HS

Title: Application of machine mearning to solid state spectroscopy and astroparticle data analysis

Abstract: In the lecture, I will present a “turnkey example” of a convolutional NN implemented with the Tensorflow library in Python. For this purpose, we will use a toy dataset and study the learning curves evolution during the model training. The final goal will be to understand how to fine-tune the parameters of a such NN in a hands-on approach.

10.02.2023, 10:00 am

Prof. Dr. Leonetta Baldassarre - Department of Physics, Sapienza University of Rome
i-RTG Lecture in Röntgen-HS

Title: Infrared and Raman spectroscopies in solids as a way to study both vibrational and electronic properties

Abstract:

Raman and infrared (IR) are two complementary vibrational spectroscopy techniques that enable label-free, noninvasive, and nondestructive structural characterization of analyzed samples. For molecular systems, both these techniques allow for chemical recognition and, by introducing molecule-specific strong light-matter interaction at mid-infrared wavelengths through the engineering of plasmonic effects, one can target the development of lab-on-chip sensors.
In crystalline samples, infrared spectroscopy provides a direct measure of the spectrum of excitations that display a modification of the dipole moment, it is thus possible to identify the signatures of the free-carriers, and of collective excitation as charge density waves.
Raman spectroscopy relies instead on the inelastic scattering of photons and is used to observe vibrational, rotational, and other low-frequency excitations displaying a change in the polarizability. A different situation is found when instead one studies resonant processes, i.e. those Raman processes involving an electronic transition between two real states of the system under exam (and not to a virtual state): therein an enhancement of the Raman cross-section occurs with respect to non-resonant processes. Thanks to the resonance condition variations in the electronic properties (due to doping, defects, or strain) can be translated into a modification of the position, the width and the intensity of the Raman peaks. This means that through Raman scattering one can probe for example the effect of electron-phonon interaction.
I will briefly introduce the two experimental techniques, their latest developments in order to increase their sensitivity and lateral resolution to the nanometer scale and discuss some exemplary experiments.

09.12.2022, 10:00 am

Dr. Stephan Schröder-Köhne - Graduate School Science and Technology, Julius-Maximilians-Universität Würzburg
i-RTG Lecture in Röntgen-HS

Title: Awareness and attitude in performing research, or: Good Scientific Practice is what you make of it - Part II

Abstract: We will look at the actual national and international rules of Good Scientific Practice in some detail, and we will talk about procedures how to deal with issues of GSP formally and practically. After a coffee break we will discuss case studies (group work). Participants please bring along a smartphone/tablet and download the App “Dilemma Game“ (Erasmus Universiteit Rotterdam), available for iOS and Android.

20.09.2022, 10:30 am

Prof. Dr. Peter Krüger - Department of Materials Science, Chiba University, Chiba, Japan
i-RTG Lecture in HS P (Roentgen HS)

Title: Circular dichroism in ARPES and the role of final state electron scattering.

29.07.2022, 10:30 am

Prof. Pavel Jelinek - Czech Academy of Sciences
i-RTG Lecture in HS P

Title: TBA

15.07.2022, 10:30 am

Prof. Stephan Rachel, University of Melbourne, Australia
i-RTG Lecture in Röntgen-HS

Title: Realization of a discrete time crystal on IBM’s quantum computer

10.06.2022, 10:30 am

Dr. Sander Smink - Max-Planck-Institut für Festkörperforschung
i-RTG Lecture in HS P

Title: Epitaxial growth of quantum materials – Overview and state of the art

Quantum materials present real-life realizations of physical concepts that are of tremendous interest both for fundamental research and for technological applications. High-quality single crystals of such materials allow the study of their physical properties, but growing them as thin films allows tuning these properties effectively – e.g, through strain, light, electric/magnetic fields, and chemical reactions. Such tuning enables us to establish fundamental connections between their properties (e.g., the critical temperature for superconductivity and charge carrier density) and is the first step towards applying these properties in functional technology.

Epitaxial growth is the key to depositing high-quality films of quantum materials. We speak of epitaxial growth if the crystallographic orientation of the grown film has a well-defined relation to that of the substrate on which it is grown. This lecture consists of two parts: in the first, I introduce epitaxy in a general sense, discussing relevant physical processes and parameters, and diagnostic tools for assessing it. In the second part, I present an overview of techniques used for epitaxial growth, discussing their individual strengths and limits and presenting state-of-the-art examples of their application. The aim of this lecture is to inform students and early-career researchers about the possibilities of using epitaxial growth for their research interests, and to review the state of the art and current challenges for all who are interested.

03.06.2022, 10:30 am

Prof. Samir Lounis  - Forschungszentrum Jülich
i-RTG Lecture in HS P

Title: Overview of spontaneous and externally-driven quantum spin fluctuations of adatoms: a first-principles perspective

06.05.2022, 10:30 am

Dr. Lukasz Plucinski  - Forschungszentrum Jülich
i-RTG Lecture in HS P

Title: Simple Models of Topological Materials

24.01.2020, 10:30 am

Prof. Stefan Tautz - Forschungszentrum Jülich
Brainstorming Session in HS P

Title: The Role of Spectroscopy in the Realization of Topological Quantum Computing

17.01.2020, 10:15 am

Federico Cilento Elettra - Sincrotrone Trieste S.C.p.A. Italy
i-RTG Lecture in HS P

Title: Table-top time-resolved spectroscopies for complex materials

Abstract:

Time-resolved spectroscopies have emerged as fundamental spectroscopic tools for probing complex materials, to both investigate ground-state-related properties and trigger phase transitions among different states with peculiar electronic and lattice structures. In recent years, they have been used to shed light on a large variety of open issues on the physics of complex and strongly-correlated materials. In particular, time-domain measurements have been widely used to disentangle, by their different timescales, the degrees of freedom of a system that at equilibrium are intertwined, thus advancing the comprehension of ground state properties of solid state compounds. Moreover, photoexcitation at high enough fluence makes it possible to trigger phase transitions among different states of a sample, often not attainable under equilibrium conditions, allowing to achieve a true ultrafast control over the functional properties of materials.

Here I will report on a number of science cases where the non-equilibrium approach allowed to advance the comprehension of the materials properties, and show the latest science-driven advancements in the fields of time-resolved optical and photoelectron spectroscopies from table-top ultrafast light sources. Finally, I will discuss how table-top spectroscopies can complement experiments at large-scale facilities, including Synchrotron Radiation Sources and Free Electron Lasers.

10.01.2020, 10:15 am

Prof. Dr. Wulf Wulfhekel - Physikalisches Institut, KIT, Karlsruhe
i-RTG Lecture in HS P

Title: Design principles, challenges and techniques for scanning tunneling microscopy at mK temperatures

Abstract:

Scanning tunneling microscopy (STM) and spectroscopy (STS) at temperatures in the mK regime requires special efforts. These include restricted design rules for cryostats capable to reach these temperatures in combination with low vibrations and long standing times. Often, the designs lead to machines that are difficult to handle. We will discuss, how to circumvent some of the pitfalls of common designs. To reach the necessary quality of electric signals and the thermalization of the electron temperature, special care has to be taken for many of the signal lines. We will introduce some of the techniques based on a 30mK design at KIT and will show, what trade-offs have to be taken and how the signal quality influences the measuring protocols at ultra-low temperatures.

13.12.2019, 10:15 am

Dr. Georg Rohringer - University of Hamburg
i-RTG Lecture in HS P

Title: Two-particle self-consistency and conservation laws in strongly correlated electron systems.

Abstract:

In the lecture, I will discuss in detail the two-particle self-consistency relations and the conservation
laws for the basic model for strongly correlated electron systems, i.e., the Hubbard model. More
specifically, I will present I derivation of the equations of motion which connects the full two-particle
vertex function with the self-energy. Then I will show, how the requirement of charge conservation
leads to a constraint for the one-particle self-energy and the two-particle irreducible vertex. The final
part of the lecture will address the question how in general approximate theories can be constructed
which fulfill either the equation of motion and the Pauli principle[1] or the conservations laws[2].

[1] G. Rohringer et al., Rev. Mod. Phys. 90, 025003 (2018).
[2] G. Baym and Leo P. Kadanoff, Phys. Rev. 124, 287 (1961).

06.12.2019, 10:15 am

Prof. Dr. Carsten Timm - TU Dresden
i-RTG Lecture in HS P

Title: Group-theoretical analysis and synthesis of Hamiltonians

Abstract:

The purpose of this lecture is to show how group theory can be used to analyze model Hamiltonians and also to construct such Hamiltonians based on symmetries. It should help to answer questions such as the following: Why did the authors of paper X write down this weird Hamiltonian? Is the model used in paper Y generic for systems of the relevant symmetry or does it contain hidden approximations? How can I construct a model Hamiltonian for some complicated lattice? Which symmetries of superconducting states are possible for a certain system?
 

Lecture Notes

29.11.2019, 10:15 am

Prof. Dr. Claude Monney - University Of Fribourg
i-RTG Lecture in SE7

Title: Lecture on RIXS

Abstract:

This lecture will be devoted to the basics of resonant inelastic x-ray scattering (RIXS). RIXS is a powerful and versatile modern x-ray spectroscopy. We will derive together the Kramers-Heisenberg formula describing RIXS using second-order perturbation theory. We will then discuss how a RIXS experiment is planned in practice, taking advantage of the absorption edge of relevant ions in materials to be chemically sensitive and of the scattering geometry to enhance its selectivity.

In the last 10 years, the development of the RIXS technique and its application to correlated materials followed a steady and impressive progress. We will therefore illustrate the lecture with examples from the recent scientific literature and discuss them in details. For that purpose, we will show how RIXS can measure crystal field excitations, magnetic excitations or interband electron-hole excitations.

18.10.2019, 10:15 am

Prof. Dr. Herbert Pfnür - Leibniz Universität Hannover
i-RTG Lecture in SE7

Title: Elastic and inelastic scattering of low energy electrons

Abstract: Due to their strong interaction with condensed matter, low energy electrons (1 to 500 eV) impinging on a solid surface can only penetrate very few layers before they are elastically or inelastically scat­tered. This fact not only generates high surface sensitivity, but also makes these electrons a very versatile tool for investigating both surface structure and low-energy excitations predominantly at surfaces. In this lecture I will give an overview about the various possibilities, starting with elastic, coherent electron diffraction. While long range order can mostly be dealt with in single scattering approxima­tion, short range (multiple) scattering contains all the information about the local structure, so that diffracted intensities as a function of energy and/or angle can be used to determine atomic positions at surfaces. Inelastic scattering generates characteristic excitations such as local vibra­tions of adsorbates, phonons, plasmons or electron-hole pairs. The discrimination between the various possibilities is sometimes not easy and requires the assistance of quantitative simulations. I will both discuss a few characteristic examples as well as experimental aspects.

12.07.2019, 10:15 am

Prof. Dr. CHristoph Tegenkamp - Technische Universität Chemnitz
i-RTG Lecture in SE7

Title: Electronic transport on surface structures: advantages, limitations and challenges

14.06.2019, 14:15 pm

Dr. Christian Tusche - Forschungszentrum Jülich, Peter Grünberg Institut (PGI-6)
i-RTG Lecture in SE7

Title: Principles and Applications of Spin-resolved Photoelectron Spectroscopy with the Momentum Microscope
 

29.03.2019, 11:30 am

Dr. Flavio de Souza Nogueira, IFW Dresden
i-RTG Lecture in SE5

Title: Chiral anomaly and second-quantized Berry phases

27.03.2019, 01:00 pm

Dr. Flavio de Souza Nogueira, IFW Dresden
i-RTG Lecture in SE5

Title: Haldane's topological nonlinear sigma model theory  of one-dimensional antiferromagnets

26.03.2019, 01:00 pm

Dr. Flavio de Souza Nogueira, IFW Dresden
i-RTG Lecture in SE5

Title: Nonlinear sigma models and topological action

18.01.2019, 10:15 am

Prof. Markus Donath, Universität Münster
i-RTG Lecture in SE2

Title: Putting a new spin on unoccupied electronic states

17.01.2019, 02:00 pm

Prof. Su Ning, EPFL, Lausanne, Switzerland
i-RTG Lecture in SE5

Title: Numerical conformal bootstrap II

16.01.2019, 04:00 pm

Prof. Su Ning, EPFL, Lausanne, Switzerland
i-RTG Lecture in SE5

Title: Numerical conformal bootstrap I

15.01.2019, 04:00 pm

Prof. Su Ning, EPFL, Lausanne, Switzerland
i-RTG Lecture in SE5

Title: Crash course in conformal field theory.

30.11.2018, 10:15 am

Thomasz Story, Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
i-RTG Lecture in SE2

Title: Thermoelectricity and topological materials

18.06.2018, 10:15 am

Dr. Moritz Hoesch, DESY, Hamburg,
i-RTG Lecture in SE2

Title: Momentum-resolved solid state spectroscopy using synchrotron radiation (IXS, ARPES)

15.06.2018, 10:15 am

Dr. Giancarlo Panaccione, ELETTRA synchrotron, Trieste, Italy
i-RTG Lecture in SE2

Title: From surface to bulk sensitivity via Photoelectron Spectroscopy with Synchrotron Radiation.

01.12.2017, 10:15 am

Anna Isaeva, TU Dresden
i-RTG Lecture in SE2

Title:Growth of bulk inorganic crystals: theory, tips and cheats

21.07.2017, 10:15 am

Gianni Profeta, l’Aquila, Italien
i-RTG Lecture in SE2

Title: Towards room temperature superconductivity

12.05.2017, 10:15 am

Dr. Silvia Picozzi, CNR-SPIN Chieti, Italien
i-RTG Lecture in SE2

Title: Interplay between spin and dipolar degrees of freedom

01.07.2016, 10:00 am

Prof. Dr. Markus Morgenstern, RWTH Aachen
i-RTG Lecture in SE2

Title: What we can learn about TIs from STM measurements

22.04.2016, 10:00 am

Prof. L. H. Tjeng, Max-Planck-Institute for Chemistry and Physics of Solids, Dresden
i-RTG Lecture in SE2

Title: Strongly correlated systems and their excitations: a back-of-the-envelope introduction

29.01.2016, 10:00 am

Eugene Krasovskii, Universidad del Pais Vasco
i-RTG Lecture in SE2

Title: Relativistic band structure and theory of angle- and spin-resolved photoemission