Raman scattering evidence for a cascade-like evolution of the charge-density-wave collective amplitude mode

TL;DR

This study uses Raman scattering to reveal a cascade-like evolution of charge-density-wave collective modes in rare-earth tri-tellurides, showing two sequential BCS-like transitions in the amplitude mode.

Contribution

It provides new experimental evidence of a cascade-like development of CDW amplitude modes, highlighting complex temperature-dependent behavior in these materials.

Findings

Identification of collective CDW amplitude excitations in DyTe3 and LaTe3 under pressure.

Discovery of two sequential BCS-like transitions in the amplitude mode.

Observation of a cascade-like evolution of the CDW collective mode.

Abstract

The two-dimensional rare-earth tri-tellurides undergo a unidirectional charge-density-wave (CDW) transition at high temperature and, for the heaviest members of the series, a bidirectional one at low temperature. Raman scattering experiments as a function of temperature on DyTe$_3$ and on LaTe$_3$ at 6 GPa provide a clear-cut evidence for the emergence of the respective collective CDW amplitude excitations. In the unidirectional CDW phase, we surprisingly discover that the amplitude mode develops as a succession of two mean-field, BCS-like transitions in different temperature ranges.