Termination-dependent topological surface states of the natural superlattice phase Bi_4Se_3

Abstract

We describe the topological surface states of Bi_4Se_3, a compound in the infinitely adaptive Bi_2-Bi_2Se_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_4Se_3 therefore represents the only known compound with different topological states on differently terminated, easily distinguished and stable surfaces.

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