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). [mehr]

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. [mehr]

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. [mehr]

MPSD Seminar

13667 1523535473

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

Lecture IV Abstract will follow. [mehr]

MPSD Seminar

14175 1526650641

Ultrafast Electron Diffraction and Microscopy with High-Coherence Beams

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]

MPSD Seminar

13669 1527676435

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

Lecture notes see 'more' [mehr]

MPSD Seminar

13666 1527676589

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

Lecture notes see 'more'. [mehr]

MPSD Seminar

13665 1527676604

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

Lecture notes see 'more'. [mehr]

 
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