Optical study of the multiple charge density wave transitions in ErTe$_3$

TL;DR

This optical spectroscopy study investigates the charge density wave transitions in ErTe$_3$, revealing two distinct gap features, partial Fermi surface gapping, and persistent fluctuations in this 2D material.

Contribution

The paper provides the first detailed optical analysis of multiple CDW transitions in ErTe$_3$, highlighting the partial gapping of the Fermi surface and fluctuation effects.

Findings

Two CDW gap features at 343 meV and 110 meV observed.

Approximately half of the Fermi surface remains ungapped at low temperature.

Fluctuation effects are significant in this 2D material.

Abstract

We present an optical spectroscopy study on singe crystalline ErTe$_3$, a rare-earth-element tri-telluride which experiences two successive charge density wave (CDW) transitions at T$_{c1}$ = 267 K and T$_{c2}$ = 150 K. Two corresponding gap features, centered at 2770 \cm ($\sim$ 343 meV) and 890 \cm ($\sim$ 110 meV) respectively, are clearly seen in ordered state. A pronounced Drude component, which exists at all measurement temperatures, demonstrates the partial gap character of both CDW orders. About half of the unmodulated Fermi surface (FS) remains in the CDW state at the lowest measurement temperature. The study also reveals that fluctuation effect is still prominent in this two-dimensional (2D) material.