Optical spectroscopy study of three dimensional Dirac semimetal ZrTe$_5$

TL;DR

This study uses infrared reflectivity to provide optical evidence that ZrTe$_5$ is a 3D Dirac semimetal, revealing its electronic structure and temperature-dependent plasma behavior.

Contribution

First optical spectroscopic proof confirming ZrTe$_5$ as a 3D Dirac semimetal through its linear optical conductivity.

Findings

Optical conductivity increases linearly with frequency below interband transitions.

The plasma edge shifts to lower energy with decreasing temperature.

A sharp peak indicates a Van Hove singularity in the density of states.

Abstract

Three dimensional (3D) topological Dirac materials are under intensive study recently. The layered compound ZrTe$_5$ has been suggested to be one of them by transport and ARPES experiments. Here, we perform infrared reflectivity measurement to investigate the underlying physics of this material. The derived optical conductivity exhibits linear increasing with frequency below normal interband transitions, which provides the first optical spectroscopic proof of a 3D Dirac semimetal. Apart from that, the plasma edge shifts dramatically to lower energy upon temperature cooling, which might be associated with the consequence of lattice parameter shrinking. In addition, an extremely sharp peak shows up in the frequency dependent optical conductivity, indicating the presence of a Van Hove singularity in the joint density of state.