Optical properties of the Ce and La di-telluride charge density wave compounds

TL;DR

This study investigates the optical properties of LaTe$_2$ and CeTe$_2$ charge density wave compounds, revealing the energy scale of their CDW gaps and the extensive gapping of their Fermi surfaces.

Contribution

It provides the first broad spectral electrodynamic response measurements of LaTe$_2$ and CeTe$_2$, identifying the CDW gap energy scale and the impact on the Fermi surface.

Findings

The CDW gap energy scale is established across a broad spectral range.

A large portion of the Fermi surface is gapped by the CDW state.

Interactions and Umklapp processes influence the CDW ground state.

Abstract

The La and Ce di-tellurides LaTe$_2$ and CeTe$_2$ are deep in the charge-density-wave (CDW) ground state even at 300 K. We have collected their electrodynamic response over a broad spectral range from the far infrared up to the ultraviolet. We establish the energy scale of the single particle excitation across the CDW gap. Moreover, we find that the CDW collective state gaps a very large portion of the Fermi surface. Similarly to the related rare earth tri-tellurides, we envisage that interactions and Umklapp processes play a role in the onset of the CDW broken symmetry ground state.