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arXiv · 2211.04229

Strong electron-phonon coupling and enhanced phonon Gr\"uneisen parameters in valence-fluctuating metal EuPd$_2$Si$_2$

Mai Ye·Mark Joachim Graf von Westarp·Sofia-Michaela Souliou·Marius Peters·Robert Möller·Kristin Kliemt·Michael Merz·Rolf Heid·Cornelius Krellner·Matthieu Le Tacon
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Abstract

We study the valence crossover and strong electron-phonon coupling of EuPd$_2$Si$_2$ by polarization-resolved Raman spectroscopy. The fully-symmetric phonon mode shows strongly asymmetric lineshape at low temperature, indicating Fano-type interaction between this mode and a continuum of electron-hole excitations. Moreover, the frequency and linewidth of the phonon modes exhibit anomalies across the valence-crossover temperature, suggesting the coupling between valence fluctuations and lattice vibration. In particular, two phonon modes show significantly enhanced Gr\"uneisen parameter, suggesting proximity to a critical elasticity regime. The relative contribution of the structural change and valence change to the phonon anomalies is evaluated by density functional theory calculations.

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Mai Ye, Mark Joachim Graf von Westarp, Sofia-Michaela Souliou, Marius Peters, Robert Möller, Kristin Kliemt, Michael Merz, Rolf Heid, Cornelius Krellner, Matthieu Le Tacon. 2022-11-08. Strong electron-phonon coupling and enhanced phonon Gr\"uneisen parameters in valence-fluctuating metal EuPd$_2$Si$_2$. https://doi.org/10.1103/physrevb.107.195111

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