Emergent and Tunable Topological Surface States in Complementary Sb/Bi<sub>2</sub>Te<sub>3</sub> and Bi<sub>2</sub>Te<sub>3</sub>/Sb Thin-Film Heterostructures.
basic_science · Level V
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- Record sourced from PubMed, PMID 35699943.
- Also identified by DOI 10.1021/acsnano.2c04639 and PMC identifier 9245572.
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Abstract
Epitaxial thin-film heterostructures offer a versatile platform for realizing topological surface states (TSSs) that may be emergent and/or tunable by tailoring the atomic layering in the heterostructures. Here, as an experimental demonstration, Sb and Bi<sub>2</sub>Te<sub>3</sub> thin films with closely matched in-plane lattice constants are chosen to form two complementary heterostructures: Sb overlayers on Bi<sub>2</sub>Te<sub>3</sub> (Sb/Bi<sub>2</sub>Te<sub>3</sub>) and Bi<sub>2</sub>Te<sub>3</sub> overlayers on Sb (Bi<sub>2</sub>Te<sub>3</sub>/Sb), with the overlayer thickness as a tuning parameter. In the bulk form, Sb (a semimetal) and Bi<sub>2</sub>Te<sub>3</sub> (an insulator) both host TSSs with the same topological order but substantially different decay lengths and dispersions, whereas ultrathin Sb and Bi<sub>2</sub>Te<sub>3</sub> films by themselves are fully gapped trivial insulators. Angle-resolved photoemission band mappings, aided by theoretical calculations, confirm the formation of emergent TSSs in both heterostructures. The energy position of the topological Dirac point varies as a function of overlayer thickness, but the variation is non-monotonic, indicating nontrivial effects in the formation of topological heterostructure systems. The results illustrate the rich physics of engineered composite topological systems that may be exploited for nanoscale spintronics applications.