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

MPSD Seminar

  • Datum: 04.12.2018
  • Uhrzeit: 14:00 - 15:00
  • Vortragende(r): Paulina Majchrzak
  • University of Edinburgh
  • Ort: CFEL (Bldg. 99)
  • Gastgeber: Isabella Gierz
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.

The simplest way to fabricate few-layer group 4 transition-metal dichalcogenides (TMDCs) samples is to mechanically exfoliate them from bulk single crystals. High-quality films, however, are often grown on supporting substrates, which can heavily modulate the behaviour of the charge carries in the material. In this work, we look into the transient band structure evolution of bilayer WS2 on a metallic substrate upon pumping it with ultrafast laser pulses. We consider the relative effects of substrate screening, interlayer interactions and surface quality on the relaxation pathways available to hot electrons and holes.

Light-induced spin-state switching is a prospective way to achieve faster magnetic data recording devices. Molecule-based magnets are excellent candidates to implement this scheme since they typically show rich photophysics that can be exploited by resonantly exciting specific transitions, and their optical, electrical as well as magnetic properties can be easily tuned through chemical substitutions. We investigate a series of Prussian blue analogues (PBAs) to elucidate the dynamics of various states involved in the superexchange interaction between the magnetic metal centres in these compounds.

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