Strain-induced topological phase transition at (111) SrTiO$_3$-based heterostructures

TL;DR

This paper models the electronic structure of (111) SrTiO3 heterostructures, showing how strain and spin-orbit coupling induce a topological phase transition with potential for experimental control.

Contribution

It introduces a multi-band tight-binding model that captures strain-induced topological phase transitions in SrTiO3 heterostructures, aligning with experimental observations.

Findings

Presence of a Dirac cone under strain conditions.

Spin-orbit coupling and trigonal strain induce quantum spin Hall effect.

Strain can switch the system between conducting and topological insulating states.

Abstract

The quasi-two-dimensional electronic gas at the (111) SrTiO$_3$-based heterostructure interfaces is described by a multi-band tight-binding model providing electronic bands in agreement at low energies with photoemission experiments. We analyze both the roles of the spin-orbit coupling and of the trigonal crystal field effects. We point out the presence of a regime with sizable strain where the band structure exhibits a Dirac cone whose features are consistent with \textit{ab-initio} approaches. The combined effect of spin-orbit coupling and trigonal strain gives rise to non-trivial spin and orbital angular momenta patterns in the Brillouin zone and to quantum spin Hall effect by opening a gap at the Dirac cone. The system can switch from a conducting to a topological insulating state \textit{via} modification of trigonal strain within a parameter range which is estimated to be experimentally achievable.