Mechanism of orbital reconstruction at the interfaces of transition metal oxides

TL;DR

This study investigates how orbital configurations change at the interface of YBa2Cu3O6 and SrTiO3 using LSDA+U calculations, revealing a new Cu oxidation state and orbital occupancy modifications that influence interfacial electronic structure.

Contribution

It provides a detailed theoretical analysis of orbital reconstruction mechanisms at transition metal oxide interfaces, highlighting the role of Coulomb interactions and orbital occupancy changes.

Findings

Identification of a new Cu 3d^8 oxidation state at the interface

Orbital occupancy shifts stabilize the reconstructed interface

Splitting of 3d_{3z^2-r^2} states due to Coulomb repulsion U

Abstract

Orbital reconstruction at interfaces between YBa2Cu3O6 and SrO-terminated SrTiO3 is studied using local spin density approximation (LSDA) with intra-atomic Coulomb repulsion (LSDA+U). The change of population of interfacial Cu 3d orbitals results in stabilization of a new oxidation state $3d^8$ which involves an additional modification of orbital occupancies in the nearest SrO and TiO2 layers. We find that an increase of electron charge in Cu 3d_{x^2-y^2} states counterbalances a depopulation of 3d_{3z^2-r^2} orbitals which induces, on account of the onsite Coulomb repulsion U, a splitting of 3d_{3z^2-r^2} states at CuO2-SrO interfaces.