Interplay of orbital effects and nanoscale strain in topological crystalline insulators

• Published in: Nature communications Vol. 9; no. 1; pp. 1550 - 6
• Main Authors: Walkup, Daniel, Assaf, Badih A., Scipioni, Kane L., Sankar, R., Chou, Fangcheng, Chang, Guoqing, Lin, Hsin, Zeljkovic, Ilija, Madhavan, Vidya
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19-04-2018; Nature Publishing Group; Nature Portfolio
• Subjects: 147/138; 639/301/119/2792; 639/766/119/995; Band structure; Band structure of solids; Banded structure; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Conduction; Crystal structure; Crystallinity; Electronic structure; Humanities and Social Sciences; Insulators; Microscopy; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-03887-5

Orbital degrees of freedom can have pronounced effects on the fundamental properties of electrons in solids. In addition to influencing bandwidths, gaps, correlation strength and dispersion, orbital effects have been implicated in generating novel electronic and structural phases. Here we show how the orbital nature of bands can result in non-trivial effects of strain on band structure. We use scanning–tunneling microscopy to study the effects of strain on the electronic structure of a heteroepitaxial thin film of a topological crystalline insulator, SnTe. By studying the effects of uniaxial strain on the band structure we find a surprising effect where strain applied in one direction has the most pronounced influence on the band structure along the perpendicular direction. Our theoretical calculations indicate that this effect arises from the orbital nature of the conduction and valence bands. Our results imply that a microscopic model capturing strain effects must include a consideration of the orbital nature of bands.
The role of orbital degrees of freedom in determining the electronic structure remains obscured. Here, Walkup et al. report strain-induced band structure changes in a topological crystalline insulator SnTe, whose surprising behavior reflects the  orbital nature of bands.