IMPRS Course Archive 2018

IMPRS-UFAST skills course

11224 1516104770

IMPRS Job Seminar

You are not sure yet what to do after your PhD? You want to know what kind of jobs are out there in the real world? You wonder what makes you interesting for industry? Then this seminar is the right fit for you!In this seminar you have the chance to quiz interesting people from outside of academia. Find your dream job! Or at least know where to look for it. [more]

IMPRS-UFAST Ph.D. Seminar

11077 1505816704

IMPRS-UFAST Ph.D. Seminar

[more]

IMPRS-UFAST skills course

11523 1510140940

Presentation skills

“Poets are born – speakers are made.” Public speaking is a necessity in scientific life. Take part in this 2-day course, find out what your strengths are and develop your individual presentation profile. Take steps to learn how to lead the audience from your first appearance on stage until the last question in the discussion. Be authentic, enthusiastic and convincing! [more]

IMPRS-UFAST focus course

10071 1503484768

Topological band theory - IMPRS-UFAST focus course

This course covers basic concepts in the topological classification of band structures of solids, the development of which led to the Physics Nobel Prize in 2016 for Thouless, Kosterlitz and Haldane. [more]

IMPRS-UFAST Ph.D. Seminar

12948 1518598322

Navigator workshop! Career orientation and job contacts: How to find your perfectjob outside academia

Thinking about your career after the PhD? Three half-days of explorations and personal encounters with visits to leaders from different sectors of work in Hamburg. This workshop will broaden your perspective - on what you have to offer and where you might go. [more]

IMPRS-UFAST Ph.D. Seminar

12949 1518598221

Good Scientific Practice for PhD students

In public, "good scientific practice" is often connected with cases of plagiarism when it comes to dissertations. However, the important topic covers a substatially wider spectrum of scientific conduct: Dealing with data (including checking, recording, ownership and storage), the publishing process and authorship, responsible supervision, academic cooperation, conflicts of interest and dealing with conflicts. Inappropriate academic behaviour includes inventing or faking data, violating intellectual property (theft of ideas or plagiarism) and sabotating the research of others. More subtle topics, such as skepticism, critical thinking, reproducibility, handling creativity, the danger of axiomatic assumptions and confirmation bias represent the "heart of good scientific practice". Every PhD student should have a professional understanding of all mentioned topics. [more]

IMPRS-UFAST core course

12603 1522925648

Ultrafast techniques

The course focuses on the use of modern light/ X-ray/ electron sources for investigating the physics/ chemistry/ biology phenomena. We will discuss scattering and image reconstruction techniques, spectroscopy and their use for time-resolved measurements . Key questions addressed are which techniques exist, how to use them, and which method is best used to reach a certain goal. [more]

MPSD Seminar

13735 1523627150

A New Room Temperature Multiferroic in the Bi-Fe-O System

Multiferroic materials, which exhibiting simultaneously two or more coupled ferroic orders, are attracting extensive research interest mainly due to their promising device applications in low power electronics and the exotic physics involved. Despite the fact that an increasing number of multiferroics have been identified through two decades of diligent and creative studies, their low transition temperature or small magnetoelectric coupling strength has hindered direct device applications. Searching for materials with room-temperature ferroelectricity, a large enough magnetization and coupling between these two is still the Holy Grail for fundamental condensed matter research. In this talk, I will report a novel room temperature multiferroic in the Bi-Fe-O system. The material is comprised of a hitherto-unexplored, hexagonal crystalline structure with Bi2O3 layers separated by γ-Fe2O3 blocks, which blends the excellent ferroelectric and ferrimagnetic performances of BiFeO3 and γ-Fe2O3 together to form an exotic multiferroic material with ferroelectric and ferrimagnetic transition temperature of above 760 K and 600 K, respectively. A combination of experimental and theoretical studies reveals that the polar state stems from the two dissimilar Bi sites and extends further into oxygen ions with the exquisitely modulated structure. This finding identifies a novel strategy for the realization of high-temperature multiferroicity and paves the pathway for the realization of practical room temperature magnetoelectric devices. [more]

IMPRS-UFAST core course

9959 1507719384

Non-linear optics - IMPRS-UFAST core course

The course provides an overview of the working principles of nonlinear optics with a focus on the basic physical concepts. [more]

IMPRS-UFAST core course

12947 1523274010

The theory of electronic structure and molecular dynamics

The course provides an overview of molecular electronic structure theory, covering the Hartree-Fock method, many-body perturbation theory, multiconfiguration self-consistent field, configuration interaction, coupled cluster, and density functional theory. Also it will discuss how to treat the interaction of molecules with electromagnetic fields. After this, it will cover the basics of molecular dynamics. [more]

MPSD Seminar

14106 1526396916

High-harmonic spectroscopy using bi-elliptical fields

Over the recent years, high-harmonic generation has established itself as a promising spectroscopic technique. Notable examples include the tomographic imaging of molecular wave functions [1], the tracking of nuclear dynamics [2], and the reconstruction of the attosecond time-scale electron dynamics in molecules [3, 4].All these applications, however, have been limited to laser fields with linear polarization. High harmonic generation has only recently been extended to circularly-polarized drivers by utilizing a technique known as bi-circular high-harmonic generation (BHHG) [5,6,7]. In this talk, I will demonstrate the spectroscopic applications of this technique to the study of structure and dynamics of gas-phase atoms and molecules in a self-probing manner. I will start with an analysis of the helicity asymmetry of BHHG in noble-gas atoms and then proceed by illustrating how BHHG can be applied to study dynamical symmetry-breaking in a time-dependent manner in the context of rotational and vibrational molecular motion.Extension of high-harmonic generation to the regime of highly-elliptical fields opens up the way towards the study of chiral phenomena in high-harmonic generation. In this work, circular dichroism in the range of 3-8 % is observed on randomly oriented methyl oxirane (C3H6O) molecules in the gas phase. This chiral sensitivity is attributed to the sub-cycle chiral electron dynamics involving excited states of the cation that take place during the electron continuum propagation. Finally, I will present a study of time-dependent chirality based on following the temporal evolution of circular dichroism during the course of an ultrafast photodissociation reaction. [more]

Disputation

14161 1526643739

Atomically resolved dynamics of correlated quantum systems

[more]

MPSD Seminar

14266 1528122902

Synchrotron Radiation from an Accelerating Light Pulse

Synchrotron radiation is regularly generated at large-scale facilities where GeV electrons move along kilometer-long circular paths. Here, we use a metasurface to bend light and demonstrate synchrotron radiation produced by a sub-picosecond pulse, which moves along a circular arc of radius 100 μm inside a nonlinear crystal. The emitted radiation, in the THz frequency range, results from the nonlinear polarization induced by the pulse. The generation of synchrotron radiation from a pulse revolving continuously about a circular trajectory has profound implications for on-chip THz sources. We present the first step towards this realization. [more]

MPSD Seminar

14290 1528280544

Workshop on Open Access Publishing

How can you publish via Open Access journals and boost your citations? What are GOLD and GREEN Open Access? Which science journals have Open Access or reduced fee agreements with the Max Planck Society? These and many other questions will be answered at this two-hour workshop. Open to all. To register, please mail jenny.witt@mpsd.mpg.de. [more]

MPSD Seminar

14320 1528463795

Quantum Nanoscience: Atoms on Surfaces

The scanning tunneling microscope is an amazing tool because of its atomic-scale spatial resolution. This can be combined with the use of low temperatures, culminating in precise atom manipulation and spectroscopy with microvolt energy resolution. In this talk we will apply these techniques to the investigation of the quantum spin properties of magnetic atoms sitting on thin insulating films. [more]

MPSD Seminar

14350 1528971302

Higgs mode in the d-wave cuprate superconductor Bi2Sr2CaCu2O8+δ induced by an intense THz pulse

The nonequilibrium dynamicis of the superconductors has been intensively studied over decades. Among the viriety of nonequlibrium phenomena, the study of the collective dynamics of superconducting order parameter is of essential importance, as it provides deep insights into the properties of the order parameter. Recent developments of generating intense electromagnetic pulses in the terahertz (THz) frequency range have enabled the access to low energy collective modes without giving excess energy to the system. Particularly the amplitude fluctuation of the order parameter, referred to as the Higgs mode, has been observed in a conventional s-wave superconductor Nb1-xTixN [1,2]. Its extension to unconventional d-wave superconductors is intriguing, whereas it has been nontrivial whether the Higgs mode in d-wave superconductors is observable or not. [more]

MPSD Seminar

14402 1529494756

Ultrafast pump-probe spectroscopy in the ultra violet wavelength region

Explanation of the Pump-Probe spectroscopic technique with ultrashort pulses in the ultra-violet region.Firstly, it reveals the two fundamental requirements for our experiments, which are the generation of sub-20 fs monochromatic pulses, the pump pulses, in the UV and the generation of a second broadband pulse, the probe, explaining in detail the method that we used to overcome issues and problems. Experimental setup and components are described carefully, focusing on the physics principles behind. Then some experimental data are shown for Triptophan and Azzurin, in order to try to better understand the fast processes which happen in organic molecules. [more]

MPSD Seminar

14351 1528971526

Superconductivity in single- and multi-band Hubbard models: can we optimise them?

We can capture various unconventional high-Tc superconductors basically either with single-band models or multiband ones. We can theoretically explore how we can optimise them for higher Tc's. There, "multiband" should not be confused with "multiorbital" systems, for which I shall compare merits and demerits of the two classes from both quantum many-body algorithms and materials-science points of view. For the former, I shall mention the dynamical vertex approximation to fathom the correlation between the electronic structure and the superconductivity and to search for enhanced Tc's. For the latter, I shall present various ideas that include "flat-band" superconductivity. [more]

MPSD Seminar

14352 1528971755

Higgs modes in d-wave and multi-band superconductors

Higgs mode (collective amplitude mode) in superconductors, recently detected and analysed in a conventional, s-wave superconductor, opens a novel avenue for probing the U(1) symmetry broken state. Now we have extended the notion to an unconventional, d-wave high-Tc cuprate, where a characteristic third-harmonic generation hallmarks the d-wave superconductor in a space-group resolved manner[1]. We can also predict unique features in Higgs and Leggett (phase) modes if we turn to multiband superconductors[2].[1] K. Katsumi et al, PRL 120, 117001 (2018).[2] Y. Murotani et al, PRB 95, 104503 (2017). [more]

MPSD Seminar

14806 1532601153

Ultrafast Laser-induced Kinetics in Two-dimensional Crystals

I will talk about our findings on the theory of ultrafast and ultrastrong optical field interacting with two-dimensional materials with an emphasis on honeycomb-shaped structures such as graphene. In fact, this talk is the emergence of two important and growing branches of science: ultrafast optics and 2D nanocrystals. Ultrafast optics or more specifically, attosecond science, is developed to study the quantum mechanical dynamics of electrons, both collective and individual, on atomic and molecular scales and in high-density mesoscopic systems. Recent advances in attosecond metrology and generation of ultrashort optical pulses with just a few oscillations of the electric field have provided real-time access to the motion of electrons on atomic and sub-atomic scales and opened a unique possibility for the coherent control of electron dynamics at sub-femtosecond time scale. Hence, the research and exploration of ultrafast dynamics of electrons in novel graphene-like materials under the illumination of few-cycle optical fields should prove useful to a growing community of scientists and hold promises for the future technologies especially high-speed memories, ultrafast imaging, and petahertz signal processing. [more]

MPSD Seminar

15241 1536680558

Ultrafast quasiparticle dynamics and electronphononcoupling in single-layer FeSe/SrTiO3 and(Li0.84Fe0.16)OHFe0.98Se

Distinctive superconducting behaviors between bulk and monolayer FeSe make it challenging to obtain a unified picture of all FeSe-based superconductors. Here, we investigate the ultrafast quasiparticle dynamics of an intercalated superconductor (Li1-xFex)OHFe1-ySe, which is a bulk crystal but shares a similar electronic structure with single-layer FeSe on SrTiO3. We obtain the electronphonon coupling (EPC) constant λ (0.24 ± 0.03), which well bridges that of bulk FeSe crystal and single-layer FeSe/SrTiO3 [1]. Moreover, we find that such a positive correlation between λ and superconducting Tc holds among all knownFeSe-based superconductors, even in line with reported FeAs-based superconductors. Our observation indicates possible universal role of EPC in the superconductivity of all known categories of iron-based superconductors, which is a critical step towards achieving a unified superconducting mechanism for all iron-based superconductors.References:[1] Y. C. Tian, W. H. Zhang, F. S. Li, Y. L. Wu, Q. Wu, F. Sun, G. Y. Zhou, L. L. Wang, X. C. Ma, Q. K. Xue, Jimin Zhao, Ultrafast dynamics evidence of high temperature superconductivity in single unit cell FeSe on SrTiO3. PRL 116, 107001 (2016). [more]

MPSD Seminar

15168 1536071358

California New Age Physics: Sunshine, Crystals, and Quantum Geometry of Bands

Nonlinear optical properties of materials are important as tools in basicresearch and optical technology. Recently there has been a tremendousupsurge of interest in optical nonlinear effects, especially in crystals with curvedbandstructure geometry. Such materials are candidates for applications basedon the conversion of light to dc current. In this talk I describe our discovery thata family of Weyl semimetals has by far the largest second-order susceptibility ofany previously known crystal. In puzzling over this result, we uncovered asurprising theorem relating the strength of optical nonlinearity to a quantuminvariant property of the bandstructure that unites nonlinear optics with thecelebrated “modern theory of polarization.” This quantum invariant provides anew strategy for algorithmic computational searches for nonlinear materialswith optimal response functions. [more]

MPSD Seminar

15167 1536071247

Strain tuning of quantum materials

In this talk I will discuss the development of novel methods of applying uniaxialpressure to single crystals of quantum materials. Much of our work so far hasbeen on ruthenates, but I will also mention projects on other materials. I willshow that it is now possible to strain single crystals, reversibly, to change latticeparameters by at least 1%, and that this provides a ‘tuning energy scale’equivalent to the Zeeman energy of magnetic fields of well over 1000T. Uniaxial techniques are particularly suited to controlled tuning throughLifshitz transitions, and are also a useful complement to epitaxial strain in thenfilms, which is usually biaxial. [more]

MPSD Seminar

15343 1536838669

Study of pressure-induced abnormal ice growth and multipath water-ice transition with dynamic diamond anvil cell

Water, due to its unique hydrogen bonds, is one of the materials exhibiting diverse phases, crystal morphologies, and phase transformation. As a result of interplay between environmental conditions and molecular kinetics, more than 25 crystalline and amorphous ices have been reported with various growing morphologies from polyhedron to needle. Dynamic diamond anvil cell (dDAC), which may simply resolve the interference of macroscopic driving force and microscopic kinetics by changing compression rate, is essential to study complex phase transition behaviour of water. In the present study, we haveinvestigated the effect of compression rate on crystal growth and the multiple freezing-melting pathways of H2O under far-from-equilibrium condition by using dDAC at room temperature. First, we reveal the origin of shock growth of ice VI single crystal. Under rapid compression (strain rate > ~0.1 /s), we observed a morphological transition in ice VI growth from three-dimension (3-d) to twodimension (2-d) with one-order higher growth speed. It is found that local growth condition and interface kinetics can be affected by compression rate, which facilitate the 2-d shock growth. Secondly, we explore five different pathways of freezing and melting of deeply supercompressed water and ice via metastable phases. We will discuss the mechanism of freezing and melting by calculating driving force and interfacial free energy based on the classical nucleation theory, and comparing structure of supercompressed water and stable and metastable ices obtained from Raman spectroscopy. [more]

MPSD Seminar

15344 1536838877

Experimental study of carbon nanotube resonator

In recent years, due to the maturity of micro-nano fabrication technology, artificial nano-structures are widely studied, people actively explore the mechanical, thermal, optical and electromagnetic properties in a variety of nano-materials, among which the nano-mechanical resonator draws great attention for its potential use to study the light-matter interactions. In this presentation, I will first report our experimental results of two carbon nanotube mechanical resonators that are strongly coupled when the frequencies of them are tuned very close to each other. The vibrations of the two resonators superpose to produce a frequency splitting phenomenon, indicating a strong coupling regime. Second, a parametric strong coupling between two different modes within single mechanical resonator in linear regime of small amplitudes will be presented, which is different from the strong modes coupling in nonlinear regime. Finally, I will show that a back-and-forth coherent exchange of phonon energy in two different vibration modes, to realize a classical Rabi oscillations. [more]

IMPRS-UFAST focus course

14863 1533126882

Brief overview of Quantum Dissipative Systems: techniques and applications

This course covers an operational introduction to the dissipative quantum systems. Starting with a descriptive introduction we will introduce four essential techniques: I.Liouville Equation II.Generalized Master Equation III.Lindblad Equation and IV.Equations of motion approach, each of them will be illustrated with the help of following examples: driven quantum dot/ phonon which is an essential prototype for condensed matter systems and Jaynes Cummings model borrowed from quantum optics literature. Measurable observables relevant to experiments will be discussed. [more]

MPSD Seminar

15741 1539608230

Michael Bonitz - Femtosecond electron dynamics in strongly correlated finite systems

[more]

MPSD Seminar

15553 1538124042

In Celebration of Basic Science: From the First Atomic Movies of Strongly Driven Phase Transitions to Star Trek Surgery

The 2018 European Physical Society Award Lecture for Research in Laser Science and Applications: The Picosecond Infrared Laser (PIRL) Scalpel: Achieving Fundamental (Single Cell) Limits to Minimally Invasive Surgery and Biodiagnostics. Followed by: The Future of PIRL Technology: Presentations and Round Table Discussion [more]

MPSD Seminar

15742 1539615484

Elisa Palacino Gonzalez - Molecular Photodynamics of Open Quantum Systems. Simulation of Nonlinear Optical Spectroscopies using Nonperturbative Approaches

The theoretical description of nonlinear optical spectroscopy has traditionally been laid in the framework of perturbation theory. Within this formalism, an intuitive approach to the understanding of the dynamics of a molecular system excited by several external laser pulses is based on the concept of nonlinear response functions. However, as the system complexity increases or nontrivial dynamic effects have to be taken into account (nonadiabatic interstate couplings, bath-induced relaxation) the perturbative approach becomes computationally expensive. To tackle this scenario nonperturbative approaches based on the numerically exact solution of quantum equations of motions have been developed. [more]

MPSD Seminar

15808 1539873705

Exploring and Exploiting Photoacids to Reveal Ultrafast Hydrogen Bond and Proton Transfer Dynamics in Solution: How to Move from the Mid-IR to the Soft-X-Ray Regime

Elementary steps of proton transfer between acids and bases occur on ultrafast time scales. To elucidate the microscopic mechanisms of proton transfer many research groups have applied time-resolved spectroscopy utilizing a class of organic molecules called photoacids. In this talk I will provide an overview of results obtained by my research team on photoacid molecules with ultrafast infrared spectroscopy as a local probing technique. Whereas profound insight in aqueous proton transfer pathways in acid-base neutralization have been achieved in recent years, the underlying reasons for photoacidity have remained unsolved. Recent developments will be discussed how to tackle this unsolved question using the technique of soft-x-ray spectroscopy as an alternative local probe. For this liquid flatjet technology appears to be a highly promisingmethodological approach. [more]

MPSD Health Seminar

15694 1539066993

Resilience: scientific background and its implications for our every-day life

Resilience and burnout both are not well defined concepts. But whereas theories about the development of a burnout-syndrom stress pathological pathways, theories about resilience are based on the concept of salutogenesis: two sides of thesame coin? [more]

MPSD Seminar

15877 1540388639

DIALS for ED: Adapting X-ray software for electron diffraction integration

In recent years, electron diffraction has arisen as an alternative to X-ray diffraction for structural studies on threedimensional crystals. Promising features of the technique include complete data sets from a few or even singlenanocrystals, sensitivity to the charged state of ions and the relatively low expense of the apparatus. Experimentalprotocols and detector technologies are improving, so that data collection using the rotation method, dominant inX-ray crystallography, is now feasible in a cryoTEM. This convergence of experimental techniques has beenaccompanied by repurposing of analysis tools: robust and sophisticated algorithms developed over decades forX-ray diffraction integration software can be now employed to tackle electron diffraction data. Nevertheless, thegeometry of the electron diffraction experiment incurs specific challenges to address in the analysis. Here, thediffraction integration package DIALS is discussed, highlighting particular adaptations that were made to thesoftware for various example cases of electron diffraction, particularly on protein crystals. The experience gainedindicates that integration of good quality ED data can be straightforward, but the bottleneck remains with collectionof such good data, which relies on careful calibration and understanding of the instrument. Improved apparatus willameliorate this issue and future studies to develop improved models for details including dynamic diffraction andabsorption are anticipated. [more]

IMPRS-UFAST core course

15934 1540562225

Basics of chemistry and biochemistry - IMPRS-UFAST core course

  • Start: Nov 6, 2018 10:00
  • End: Nov 15, 2018 13:30
  • Speaker: Melanie Schnell, Marta San Valls and Sam Horrell
  • In this course, chemistry will mainly be understood as reactions. The course gives an overview about the basics of reaction chemistry and discuss what is already known and what can be measured in the laboratory nowadays (i.e. describing the current frontiers and where the research performed at CFEL can make a difference). In the biochemistry part, the basic principles of nucleic acids (DNA, RNA, their replication etc.) and proteins, their structure and function etc. will be discussed. It will be interesting to work out where the new coherent sources can advance the field.
  • Location: CFEL (Bldg. 99)
  • Room: Seminar Room O1.060
  • Host: IMPRS-UFAST

[more]

IMPRS-UFAST focus course

15128 1540562286

Photoinduced Energy and Electron Transfer in the Natural and Artificial Systems

One of the most active areas of research is to assemble rationally tailored components at molecular level, which can capture the sunlight energy and transfer it in the desired directions. Biological protein systems, such as the antenna complexes, transfer the absorbed solar energy with unit efficiency into the reaction center, where the charge separation directs the water splitting. This course will provide an introduction to the processes of energy and electron transfer with the help of examples from natural photosynthetic complexes and organic photovoltaics. [more]

MPSD Seminar

16108 1542207560

Ultrafast control of matter by high-field terahertz pulses

Terahertz interaction with matter has become one of the hottest topics in ultrafast community. Indeed, intense terahertz pulses have recently proved to be a pivotal tool to manipulate and control the properties of materials and especially complex condensed matter systems. The recent development of terahertz sources driven by lasers and accelerators has led to pioneering experiments demonstrating the access to new metastable phases of matter and nonlinear processes hindered to conventional laser excitation.In this talk, I will give an overview on the high-field terahertz generation and present the capabilities of the nonlinear terahertz spectroscopy. Recent experiments, including terahertz driven insulator-to-metal transition, nonlinear optical processes and coherent phonon control, are discussed. [more]

MPSD Health Seminar

16054 1541756573

1st MPSD HEALTH DAY

Invitation to the 1st MPSD HEALTH DAY [more]

MPSD Seminar

16198 1542719197

An introduction to coupled-cluster theory, and recent developments in quantum embedding

Coupled-cluster theory has become a key tool in quantum chemistry, providing gold-standard accuracy for ground- and excited-state energetics, and other properties. [more]

IMPRS-UFAST focus course

15106 1542708944

Hubbard Model

The Hubbard model is the drosophila of condensed matter physics. It is perhaps the simplest possible model capturing the competition between localization of electrons in solids due to Coulomb repulsion and delocalization in energy bands due to kinetic energy lowering. Invented in the early 1960s to descibe magnetism in transition-metal monoxides, it has been generalized and applied to a host of problems in condensed matter including heavy fermions or high-temperature superconductors. Despite its apparent simplicity it shows complicated phase diagrams that depend on dimensionality and lattice coordination as well as electronic filling, with only few exact solutions in limiting cases known to this date. [more]

MPSD Seminar

16745 1543402156

Ultrafast dynamics in condensed matter: from 2D materials to molecular magnets

The key to designing modern optoelectronic and magnetic functional materials lies in understanding how the charge carriers respond to the excitation on ultrafast timescales – tens or hundreds of femtoseconds. In this talk, I will introduce two projects which attempt to shed light on the fundamental processes behind the remarkable physics of two-dimensional materials and molecular magnets, and how we can control them. [more]

MPSD Seminar

16665 1543492206

Nano Surface Science and Engineering for Energy Conversion and Diamond Transistors

Nano science and technology offer a vast and fascinating playground
to explore the novel physiochemical properties of nanomaterials with the development for various applications including energy conversion and electronics. [more]

MPSD Seminar

16936 1543930707

New Methods of Measuring Material Structure Using X-Ray Diffraction Data

In this talk I will discuss how the classical theory of x-ray diffraction can be used to simulate the intensity pattern produced by a powdered sample, generalised to the case where the finite size of the crystallites in the sample is accounted for. I will then explain how we are using this theory to develop new methods of measuring the shape and size of crystallites in a fractured crystal sample from x-ray diffraction data. [more]

MPSD Seminar

16884 1543579363

A time domain perspective on electron-boson coupling in superconducting materials

Experiments in the time domain allow to determine the electron-boson coupling strength by analyzing the second moment of the Eliashberg function α2∙F(ω) using the relaxation time constant of thermalized, hot electrons after optical excitation. [1] While this approach works well for conventional superconducting materials, it is under discussion for unconventional superconductors due to competing electron and boson dynamics on similar time scales. [2,3] [more]

IMPRS-UFAST core course: Non-linear optics

16194 1542709013

Non-linear optics

Nonlinear optics (NLO) is one of the most fascinating fields of modern physics. It deals with light-matter interactions at extreme electro-magnetic field strengths. Such fields are today routinely available thanks to laser technology. NLO started with the observation of second harmonic generation from a ruby laser in 1961, just 1 year after the first laser was operated. It allows producing optical pulses with durations in the femtosecond (fs, 10-15 s) and even attosecond (as, 10-18 s) order. With such sources, one can observe chemical reactions, physical and biological phenomena in real time. During the lectures, I will give a short overview of NLO. I will discuss the main physical phenomena (second harmonic generation, optical parametric amplification, difference and sum frequency generation, white light generation, third harmonic generation, high harmonic generation…) and some of their applications, and conclude with the newest trends of research like coherent pulse synthesis. [more]

MPSD Seminar

16937 1544611408

Charge density wave (CDW) order in monolayer TMDs

Charge density wave (CDW) ordering and the mechanism for it remains a live issue, particularly in transition-metal dichalcogenide (TMD) systems. These are attractive because of both the variety of material properties they are known to host, and their conveniently layered van der Waals structures. The evolution of properties and interactions of these materials when thinned to a monolayer limit remains an area for exploration. In this talk, I present some background on the study of CDW order in bulk and monolayer TMDs. I then discuss some recent results, as well as my own upcoming investigations of TiTe2, utilising molecular beam epitaxy (MBE) growth and photon energy-dependent angle resolved photoemission spectroscopy (ARPES). [more]

 
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