Revealing a charge-density-wave gap in the predicted weak topological insulator HoSbTe

TL;DR

This study uses infrared spectroscopy to reveal a charge density wave gap in HoSbTe, a predicted weak topological insulator, showing coexistence of CDW and spin-orbit coupling gaps and providing new insights into its electronic properties.

Contribution

It is the first to experimentally identify a charge density wave gap in HoSbTe, demonstrating coexistence with the SOC gap in this weak topological insulator.

Findings

HoSbTe exhibits metallic behavior from 350 K to 10 K.

A charge density wave gap of 364 meV at 10 K was observed.

The CDW gap shifts from 252 meV at 350 K to 364 meV at 10 K.

Abstract

HoSbTe was predicted to be a weak topological insulator, whose spin-orbit coupling (SOC) gaps are reported to be as large as hundreds of meV. Utilizing infrared spectroscopy, we find that the compound is of metallic nature from 350 K down to 10 K. Particularly, both of its itinerant carrier density and scattering rate are demonstrated to decrease with temperature cooling, which is responsible for the appearance of a broad hump feature in the temperature dependent resistivity around 200 K. More importantly, we reveal the appearance of a charge density wave (CDW) gap in addition to the SOC related gap. The energy scale of the CDW gap is identified to be 364 meV at 10 K, which shift to 252 meV at 350 K. The coexistence of CDW and SOC gaps in the same compound paves a new avenue to explore more intriguing physics.