Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 25: Poster

KFM 25.21: Poster

Donnerstag, 8. September 2022, 15:00–18:00, P2

Strong electron-phonon coupling in EuPd2Si2 — •Mai Ye1, Mark Joachim Graf von Westarp1, Sofia-Michaela Souliou1, Marius Peters2, Robert Möller2, Kristin Kliemt2, Cornelius Krellner2, and Matthieu Le Tacon11Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany — 2Institute of Physics, Goethe-University Frankfurt, 60438 Frankfurt am Main, Germany

Mixed-valence metal EuPd2Si2 exhibits a valence transition from Eu2+ to Eu3+ with the crossover temperature Tv around 140 K [Jpn. J. Appl. Phys. 50 (2011) 05FD03]. On cooling, the tetragonal crystal symmetry is unchanged, with the a-axis length decreasing and the c-axis length essentially unchanging [arXiv:2203.05136]. We study the phonon modes of this material by Raman spectroscopy to explore the effect of valence transition and electron-phonon coupling. The Raman-active A1g phonon mode shows Fano-type asymmetric lineshape, indicating interaction between the phonon mode and underlying continuum of electronic excitations. This mode also exhibits large frequency hardening on cooling: the frequency at 25 K is around 30% larger than that at 300 K. Such a large frequency change cannot be solely explained by the change of lattice parameters, which is only 2%, and points to the role played by electron-phonon interaction. Moreover, the frequency and linewidth of other Raman-active phonon modes show anomalies at Tv. We also present Raman spectra of EuPd2(Si0.94Ge0.06)2 for comparison.

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