Electron degeneracy and intrinsic magnetic properties of epitaxial Nb:SrTiO$_3$ thin-films controlled by defects

TL;DR

This study demonstrates how defect management during growth can lift electronic band degeneracy in epitaxial Nb:SrTiO$_3$ thin films, leading to notable magnetic and transport phenomena, with implications for oxide electronics.

Contribution

It reveals that defect control induces band splitting and magnetic properties in epitaxial SrTiO$_3$ films, a novel approach to tuning oxide electronic behavior.

Findings

Defect management lifts electronic band degeneracy.

Epitaxial stress causes tetragonal distortion and magnetic effects.

Transport properties show Kondo-like resistance upturn and anisotropic magnetoresistance.

Abstract

We report thermoelectric power experiments in e-doped thin films of SrTiO$_3$ (STO) which demonstrate that the electronic band degeneracy can be lifted through defect management during growth. We show that even small amounts of cationic vacancies, combined with epitaxial stress, produce a homogeneous tetragonal distortion of the films, resulting in a Kondo-like resistance upturn at low temperature, large anisotropic magnetoresistance, and non-linear Hall effect. Ab-initio calculations confirm a different occupation of each band depending on the degree of tetragonal distortion. The phenomenology reported in this paper for tetragonally distorted e-doped STO thin films, is similarto that observed in LaAlO$_3$/STO interfaces and magnetic STO quantum wells.