Archiv 2019

Gastgeber: Michael Först / Andrea Cavalleri

Cooperative valence dynamics in Anderson Lattices observed by resonant inelastic x-ray scattering

MPSD Seminar
In rare earth intermetallics with weakly bound f-electrons and a Kondo energy scale much larger than magnetic exchange interactions or crystal field splittings, the screening of local moments may result in a non-magnetic Fermi liquid ground state [1]. At low temperatures, the quantum fluctuations between magnetic and non-magnetic valence configurations can then acquire a cooperative (lattice) character. On a phenomenological basis, a sound understanding of this Anderson Lattice phenomenon has been achieved. On the other hand, the microscopic description of the coherent coupling between Kondo-screened sites remains an outstanding theoretical challenge [2]. In experiment, the cooperative character of Anderson Lattices has only recently become directly accessible. Momentum-resolved spectroscopies, such as angle-resolved photoemission and inelastic neutron scattering, reveal the emergence of characteristic low-energy quasiparticle dynamics at low temperatures [3]. These methods probe single-particle excitations in the charge and magnetic channels, respectively. By contrast, high-resolution resonant inelastic x-ray scattering (RIXS) experiments couple to both charge and spin degrees of freedom in a non-trivial way and thus provide a more subtle point of view. If calculations of the underlying Kramers-Heisenberg term on a basis of strongly correlated f-electronic bands are achieved, RIXS may unlock unprecedented microscopic insights into the entanglement of local and itinerant charge and magnetic degrees of freedom. This would address a fundamental mechanism of quantum matter, with relevance far beyond lanthanides and actinides. I will review previous spectroscopic investigations of intermediate valence materials, present our recent RIXS results on the archetypal Anderson Lattice compound CePd3, and highlight some ideas for future x-ray scattering studies at 3rd and 4th generation light sources. [mehr]

Single-shot optical probing of laser-generated plasmas

MPSD Seminar
Lasers have captured scientific interest since their inception and increase in the on-target intensity has resulted in powerful petawatt (≈1015W) laser systems across the globe [1]. Such a laser gives the possibility to study and optimize processes such as electron [2] or ion [3] acceleration resulting from interaction of extreme electric fields (E ≥ 0.5 TV/m) with matter 0. In this talk, I would outline the current efforts of POLARIS (a Petawatt laser system) in Jena to study the effects of such laser-plasma interaction. A single-shot all optical probing was performed with Aluminum targets to fully characterize the plasma evolution. The basic motivation of the work, the experimental setup used and some results would be presented in the talk. [mehr]
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