Optical properties of the charge-density-wave polychalcogenide compounds $R_2$Te$_5$ ($R$=Nd, Sm and Gd)

TL;DR

This study explores the optical properties of rare-earth polychalcogenide compounds $R_2$Te$_5$ ($R$=Nd, Sm, Gd), revealing how their charge-density-wave gaps evolve with chemical compression, affecting their electronic structure.

Contribution

It provides the first optical analysis of $R_2$Te$_5$ compounds, showing the progressive closing of the CDW gap with lattice compression, extending understanding from related $R$Te$_n$ families.

Findings

CDW gap energy is extracted from absorption spectra.

Lattice compression leads to a closing of the CDW gap.

Metallic component is moderately enhanced with chemical compression.

Abstract

We investigate the rare-earth polychalcogenide $R_2$Te$_5$ ($R$=Nd, Sm and Gd) charge-density-wave (CDW) compounds by optical methods. From the absorption spectrum we extract the excitation energy of the CDW gap and estimate the fraction of the Fermi surface which is gapped by the formation of the CDW condensate. In analogy to previous findings on the related $R$Te$_n$ (n=2 and 3) families, we establish the progressive closing of the CDW gap and the moderate enhancement of the metallic component upon chemically compressing the lattice.