Raum: Seminar Room I-II, EG.076-078
10479 1500033194
Spectroscopic mapping by STEM/EELS has proven to be a powerful technique for determining the structure, chemistry and bonding of interfaces, reconstructions, and defects. So far, most efforts in the physical sciences have focused on room temperature measurements where atomic resolution mapping of composition and bonding has been demonstrated [1-3]. For many materials, including those that exhibit electronic and structural phase transitions below room temperature and systems that involve liquid/solid interfaces, STEM/EELS measurements at low temperature are required. Operating close to liquid nitrogen temperature gives access to a range of emergent electronic states in solid materials and allows us to study processes at liquid/solid interfaces immobilized by rapid freezing [4,5]. [mehr]

Hideo Aoki - Quantum phases induced by polarised light --- Floquet-topological states and Higgs modes

MPSD Seminar
Putting materials out of equilibrium can produce new quantum phenomena. When driven by a circularly-polarised laser, a massless Dirac system such as graphene can be converted into the Floquet topological insulator of photon-dressed electrons, which realises the quantum anomalous Hall effect. The phase diagram becomes increasingly intricate for lower laser frequencies where transitions between different Chern numbers take place. If we consider electron correlation, we can predict transitions between Floquet topological insulators and Mott insulator[1]. In another avenue a linearlypolarised light can induce the collective Higgs amplitude mode in superconductors, a condensed-matter analogue of the renowned particle. Then a resonantly strong third-harmonic generation arises, where the Higgs mode contribution is shown to dominate[2] unlike in the BCS approximation.[1] T. Mikami et al, Phys. Rev. B 93, 144307 (2016).[2] R. Matsunaga et al, Phys. Rev. B 96, 020505(R) (2017). [mehr]

Short Course on: Ultrafast Spectroscopy of Phonons and Spin Excitations in Solids - Lecture I

MPSD Seminar
Lecture notes see 'more'. [mehr]

Short Course on: Ultrafast Spectroscopy of Phonons and Spin Excitations in Solids - Lecture II

MPSD Seminar
Lecture notes see 'more'. [mehr]

Short Course on: Ultrafast Spectroscopy of Phonons and Spin Excitations in Solids - Lecture III

MPSD Seminar
Lecture notes see 'more' [mehr]
14175 1526650641

Ultrafast Electron Diffraction and Microscopy with High-Coherence Beams

MPSD Seminar
Time-resolved electron imaging, diffraction and spectroscopy are exceptional laboratory-based tools to trace non-equilibrium dynamics in materials with a sensitivity to structural, electronic and electromagnetic degrees of freedom. The capabilities of these approaches are largely governed by the quality of the beam of electrons used.This talk will discuss recent advances made by employing high-coherence ultrashort electron pulses from nanoscale field emitters, which substantially enhance the achievable image resolution in both real and reciprocal space. Two complementary developments with ultimate surface sensitivity and spatial resolution, respectively, will be presented, namely Ultrafast Low-Energy Electron Diffraction (ULEED) and Ultrafast Transmission Electron Microscopy (UTEM). Several recent examples of applying these methods to the observation of phase-ordering kinetics, the excitation of strongly-coupled fluctuation modes and the control of metastable states will be given. [mehr]

Short Course on: Ultrafast Spectroscopy of Phonons and Spin Excitations in Solids - Lecture IV

MPSD Seminar
Lecture IV Abstract will follow. [mehr]
20319 1568195985
A talk about how to succeed in challenging environments. Dr. Gregor Wittke, occupational psychologist shares his experience and know-how on coping with stress and high demands in the work place.The talk features a short overview of scientific findings on the topic as well as practical hands on strategies to apply in everyday life. Enjoy a mix of facts and numbers with practical thought experiments and even minimal movement exercises to gain confidence and composure or recover energy and determination.Besides those aspects concerning a helpful attitude to succeed in challenging environments and how to gain and maintain it, this talk will also include a kind of manual for delimiting yourself from an overwhelming amount of job tasks and focus on your own priorities. [mehr]
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