Termination dependent topological surface states of the natural superlattice phase Bi$_4$Se$_3$

TL;DR

This study investigates the topological surface states of Bi4Se3, a natural superlattice compound, revealing distinct topological states on different surface terminations through combined experimental and theoretical analysis.

Contribution

It is the first to demonstrate different topological surface states on differently terminated surfaces of a natural superlattice compound.

Findings

Topological surface states observed on both Bi and Se terminated surfaces.

Distinct dispersions and Kramers point energies for each surface.

Bi4Se3 uniquely exhibits different topological states on different terminations.

Abstract

We describe the topological surface states of Bi$_4$Se$_3$, a compound in the infinitely adaptive Bi$_2$-Bi$_2$Se$_3$ natural superlattice phase series, determined by a combination of experimental and theoretical methods. Two observable cleavage surfaces, terminating at Bi or Se, are characterized by angle resolved photoelectron spectroscopy and scanning tunneling microscopy, and modeled by ab-initio density functional theory calculations. Topological surface states are observed on both surfaces, but with markedly different dispersions and Kramers point energies. Bi$_4$Se$_3$ therefore represents the only known compound with different topological states on differently terminated surfaces.