Oxygen vacancies at titanate interfaces: two-dimensional magnetism and orbital reconstruction

TL;DR

This paper investigates how oxygen vacancies at titanate interfaces cause complex orbital reconstructions and induce two-dimensional magnetic states, revealing new magnetic phenomena not present in bulk SrTiO3.

Contribution

It demonstrates the role of oxygen vacancies in orbital and magnetic reconstructions at titanate interfaces using GGA+U calculations.

Findings

Oxygen vacancies induce multiorbital reconstruction involving t2g and eg orbitals.

Vacancy clustering affects the orbital and magnetic properties.

A two-dimensional magnetic state emerges at the interface, absent in bulk SrTiO3.

Abstract

We show that oxygen vacancies at titanate interfaces induce a complex multiorbital reconstruction which involves a lowering of the local symmetry and an inversion of t2g and eg orbitals resulting in the occupation of the eg orbitals of Ti atoms neighboring the O vacancy. The orbital reconstruction depends strongly on the clustering of O vacancies and can be accompanied by a magnetic splitting between the local eg orbitals with lobes directed towards the vacancy and interface dxy orbitals. The reconstruction generates a two-dimensional interface magnetic state not observed in bulk SrTiO3. Using generalized gradient approximation (LSDA) with intra-atomic Coulomb repulsion (GGA+U), we find that this magnetic state is common for titanate surfaces and interfaces.