Direct Evidence for the Dirac-Cone Topological Surface States in Ternary Chalcogenide TlBiSe2

TL;DR

This study provides direct experimental evidence that TlBiSe2 is a strong topological insulator with a large bulk band gap and a single Dirac cone surface state, highlighting its potential for room-temperature topological applications.

Contribution

First direct ARPES observation of Dirac-cone surface states in TlBiSe2, confirming its status as a strong topological insulator with the largest known bulk gap.

Findings

Identification of a non-trivial surface metallic state with X-shaped dispersion

Confirmation of a single Dirac cone at the Brillouin-zone center

Bulk band gap of 0.4 eV, the largest among known topological insulators

Abstract

We have performed high-resolution angle-resolved photoemission spectroscopy on TlBiSe2, which is a member of the ternary chalcogenides theoretically proposed as candidates for a new class of three-dimensional topological insulators. By measuring the energy band dispersions over the entire surface Brillouin zone, we found a direct evidence for a non-trivial surface metallic state showing a X-shaped energy dispersion within the bulk band gap. The present result unambiguously establishes that TlBiSe2 is a strong topological insulator with a single Dirac cone at the Brillouin-zone center. The observed bulk band gap of 0.4 eV is the largest among known topological insulators, making TlBiSe2 the most promising material for studying room-temperature topological phenomena.