We study the valence crossover and strong electron-phonon coupling of EuPd2Si2 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.
@article{arxiv.2211.04229,
title = {Strong electron-phonon coupling and enhanced phonon Gr\"uneisen parameters in valence-fluctuating metal EuPd$_2$Si$_2$},
author = {Mai Ye and Mark Joachim Graf von Westarp and Sofia-Michaela Souliou and Marius Peters and Robert Möller and Kristin Kliemt and Michael Merz and Rolf Heid and Cornelius Krellner and Matthieu Le Tacon},
journal= {arXiv preprint arXiv:2211.04229},
year = {2023}
}