# Topological states at the (001) surface of SrTiO3

## TL;DR

This paper reveals that the (001) surface of SrTiO3 hosts topological edge states due to inverted parity of electronic wavefunctions, suggesting new topological phenomena in this material.

## Contribution

Theoretical demonstration of topological edge states at SrTiO3 (001) surface arising from inverted wavefunction parity and Dirac cone dispersion.

## Key findings

- Presence of four gapped Dirac cones with anisotropic dispersion
- Existence of topological edge states at the boundary
- Predicted Josephson radiation signatures of topology

## Abstract

Defect-free SrTiO3 (STO) is a band insulator but Angle Resolved Photoemission Spectroscopy (ARPES) experiments have demonstrated the existence of a nanometer thin two-dimensional electron liquid (2DEG) at the (001) oriented surface of this compound. The bulk is a trivial insulator, but our theoretical study reveals that the parity of electronic wavefunctions in this 2DEG is inverted in the vicinity of special points in reciprocal space where the low-energy dispersion consists of four gapped Dirac cones with a tilted and anisotropic shape. This gives rise to linearly dispersing topological edge states at the one-dimensional boundary. We propose to probe these modes by measuring the Josephson radiation from gapless bound Andreev states in STO based junctions, as it is predicted that they display distinctive signatures of topology.