Effects of spin-orbit interaction and electron correlations in strontium titanate

TL;DR

This paper investigates how spin-orbit interaction and electron correlations influence the electronic structure of SrTiO$_3$, revealing potential mechanisms behind its unusual superconductivity and electronic properties.

Contribution

It demonstrates the interplay between anisotropic hopping, spin-orbit coupling, and electron correlations in SrTiO$_3$, highlighting the emergence of Mott-like states at high doping levels.

Findings

Bloch states from Ti t2g orbitals are affected by anisotropic hopping and spin-orbit coupling.

High doping leads to instability of flat-band states, resulting in Mott-like singlet correlations.

Findings may explain SrTiO$_3$'s anomalous electronic behavior and superconductivity.

Abstract

We show that the Bloch states in the conduction band of SrTiO$_3$ arise from the interplay between highly anisotropic hopping in sub-bands derived from the Ti $t_{2g}$ orbitals and spin-orbit coupling that mixes these orbitals. Because of the nearly flat-band characteristics for one of the principal axes, at sufficiently high doping these Bloch states become unstable with respect to electron interactions, resulting in Mott-like singlet correlations. These findings may be relevant to the anomalous electronic properties of SrTiO$_3$, including its unusual superconductivity.