Interplay of orbital effects and nanoscale strain in topological crystalline insulators

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, such as Jahn-Teller effect and colossal magnetoresistance. In this talk I will describe how we use a combination of STM studies and first principles calculations to reveal the mechnaism by which the orbital nature of bands can result in non-trivial effects of strain on band structure. Using quasiparticle interference we study the influence of strain on the electronic structure of a heteroepitaxial thin film of a topological crystalline insulator SnTe. By mapping 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 can be attributed to the orbital nature of the conduction and valence bands. Our results imply that a microscopic model capturing strain effects on band structure must include a consideration of the orbital nature of bands.