Evidence of 3D Dirac conical bands in TlBiSSe by optical and magneto-optical spectroscopy

TL;DR

This study provides optical and magneto-optical evidence of 3D Dirac conical bands in TlBiSSe, revealing a nearly linear optical response and describing the system with a massive Dirac model, highlighting its topological semimetal properties.

Contribution

First demonstration of 3D Dirac conical bands in TlBiSSe using optical and magneto-optical spectroscopy, with detailed modeling of the Dirac parameters.

Findings

Nearly linear optical conductivity below 0.5 eV

Massive Dirac model with a 32 meV gap

In-plane velocity parameter of 4.0×10^5 m/s

Abstract

TlBiSSe is a rare realization of a 3D semimetal with a conically dispersing band that has an optical response which is well isolated from other contributions in a broad range of photon eneries. We report optical and magneto-optical spectroscopy on this material. When the compound is chemically tuned into a state of the lowest carrier concentration, we find a nearly linear frequency dependence of the optical conductivity below 0.5~eV. Landau level spectroscopy allows us to describe the system with a massive Dirac model, giving a gap $2\Delta =32$~meV and an in-plane velocity parameter $v= 4.0\times 10^5$~m/s. % Finally, we provide a theoretical recipe to extract all parameters of the anisotropic Dirac band, including the Fermi energy and band degeneracy.