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HL: Fachverband Halbleiterphysik

HL 76: Poster IIIC

HL 76.23: Poster

Donnerstag, 19. März 2020, 15:00–17:30, P2/4OG

Transient negative thermal expansion and Poisson effect — •Marc Herzog¹, Alexander von Reppert¹, and Matias Bargheer^1,2 — ¹Institut für Physik und Astronomie, Universität Potsdam — ²Helmholtz-Zentrum Berlin für Materialien und Energie

Negative thermal expansion (NTE) and the Poisson effect have been mainly studied in thermal equilibrium. Here we discuss the two phenomena in the context of strain waves generated by ultrafast excitation of various material systems that exhibit NTE in thermal equilibrium. These materials range from simple semiconductors to various spin- or charge ordered phases such as (anti-)ferromagnets and ferroelectrics. As NTE can be generally understood from increasing entropy with decreasing volume, we discuss ultrafast entropic stresses as the driver of lattice dynamics.