SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 62: Ultrafast Dynamics of Light-Driven Systems

TT 62.1: Vortrag

Freitag, 31. März 2023, 09:30–09:45, HSZ 03

Ultrafast dynamics of spin-density wave order in BaFe₂As₂ under high pressures — Ivan Fotev^1,2, Stephan Winnerl¹, Saicharan Aswartham³, Sabine Wurmehl^3,4, Bernd Büchner^3,4, Harald Schneider¹, Manfred Helm^1,2, and •Alexej Pashkin¹ — ¹Helmholtz-Zentrum Dresden-Rossendorf, Germany — ²Technische Universität Dresden, Germany — ³IFW Dresden, Germany — ⁴Würzburg-Dresden Cluster of Excellence ct.qmat, Germany

We utilize pump-probe spectroscopy to measure the quasiparticle relaxation dynamics of BaFe₂As₂ in a diamond anvil cell at pressures up to 4.4 GPa and temperatures down to 8 K. Tracing the amplitude of the relaxation process results in an electronic phase diagram that illustrates the variation of the spin-density wave (SDW) order across the whole range of the applied pressures and temperatures. We observe a slowing down of the SDW relaxation dynamics in the vicinity of the phase transition boundary. However, its character depends on the trajectory in the phase diagram: the slowing down occurs gradually for the pressure-induced transition at low temperatures and abruptly for the thermally-driven transition. Our results suggest that the pressure-induced quantum phase transition in BaFe₂As₂ is related to the gradual worsening of the Fermi-surface nesting conditions.