Phonon modes and their association with the electronic states have been investigated for the metallic EuCu2As2 system. In this work, we present the Raman spectra of this pnictide system which clearly shows the presence of seven well defined peaks above 100~cm−1 that is consistent with the locally non-centrosymmetric {\it P4/nmm} crystal structure, contrary to that what is expected from the accepted symmorphic {\it I4/mmm} structure. Lattice dynamics calculations using the {\it P4/nmm} symmetry attest that there is a commendable agreement between the calculated phonon spectra at the Γ point and the observed Raman mode frequencies, with the most intense peak at ∼232~cm−1 being ascribed to the A1g mode. Temperature dependent Raman measurements show that there is a significant deviation from the expected anharmonic behaviour around 165~K for the A1g mode, with anomalies being observed for several other modes as well, although to a lesser extent. Attempts are made to rationalize the observed anomalous behavior related to the hardening of the phonon modes, with parallels being drawn from metal dichalcogenide and allied systems. Similarities in the evolution of the Raman peak frequencies with temperature seem to suggest a strong signature of a subtle electronic density wave instability below 165~K in this compound.
@article{arxiv.2501.05296,
title = {Evidences for local non-centrosymmetricity and strong phonon anomaly in EuCu2As2: A Raman spectroscopy and lattice dynamics study},
author = {Debasmita Swain and Mainak Dey Sarkar and Andrzej Ptok and G. Vaitheeswaran and Anushree Roy and Sitikantha D Das},
journal= {arXiv preprint arXiv:2501.05296},
year = {2025}
}