Three-dimensional topological insulator feature of ternary chalcogenide Ge2Bi2Te5

TL;DR

This paper identifies Ge2Bi2Te5 as a three-dimensional topological insulator with unique surface states and confirms its nontrivial topological properties through experimental and theoretical analysis.

Contribution

It is the first to demonstrate Ge2Bi2Te5 as a 3D topological insulator, expanding the family of topological materials beyond binary chalcogenides.

Findings

Ge2Bi2Te5 exhibits a hole-type Fermi surface at EF.

An unoccupied topological surface state with Dirac point 290 meV above EF.

Theoretical calculations confirm a nontrivial Z2 invariant.

Abstract

The exploration of novel topological insulators (TIs) beyond binary chalcogenides has been accelerated in pursuit of exotic quantum states and device applications. Here, the layered ternary chalcogenide Ge2Bi2Te5 is identified as a three-dimensional TI. The bulk electronic structure of Ge2Bi2Te5 features a hole-type Fermi surface at Fermi level EF, which dominates the transport properties. Moreover, an unoccupied topological surface state with a Dirac point located at 290 meV above EF has been observed. Theoretical calculations confirm a bulk bandgap and a nontrivial Z2 topological invariant (000;1). The present study demonstrates that the material family of layered tetradymite-like ternary compounds is an important platform to explore exotic topological phenomena.