Experimental verification of PbBi$_{2}$Te$_{4}$ as a 3D topological insulator

TL;DR

This paper provides the first experimental evidence that PbBi$_{2}$Te$_{4}$ is a three-dimensional topological insulator, characterized by a single Dirac cone and large iso-energy contours, promising for spintronic applications.

Contribution

It experimentally verifies PbBi$_{2}$Te$_{4}$ as a 3D topological insulator and calculates its topological invariants using ab initio methods.

Findings

Observation of a single surface Dirac cone via ARPES

Largest 2D iso-energy contours among known 3D TIs

Topological invariants $ ext{Z}_2$ calculated as 1

Abstract

The first experimental evidence is presented of the topological insulator state in PbBi$_{2}$Te$_{4}$. A single surface Dirac cone is observed by angle-resolved photoemission spectroscopy (ARPES) with synchrotron radiation. Topological invariants $\mathbb{Z}_2$ are calculated from the {\it ab initio} band structure to be 1; (111). The observed two-dimensional iso-energy contours in the bulk energy gap are found to be the largest among the known three-dimensional topological insulators. This opens a pathway to achieving a sufficiently large spin current density in future spintronic devices.