Long-range electronic reconstruction to a $d_{xz,yz}$-dominated Fermi surface below the LaAlO$_3$/SrTiO$_3$ interface

TL;DR

This study reveals a long-range electronic reconstruction at LaAlO3/SrTiO3 interfaces, showing a 3D Fermi surface with $d_{xz,yz}$ orbital dominance extending over at least 100 nm, which is crucial for understanding oxide interface physics.

Contribution

The paper uncovers a long-range, 3D electronic reconstruction at oxide interfaces, extending over 100 nm, with a dominant $d_{xz,yz}$ orbital character, expanding current understanding of interfacial electronic phases.

Findings

Observation of a 3D Fermi surface with $d_{xz,yz}$ orbital occupancy extending over 100 nm.

Emergence of bulk-like quantum oscillations at higher carrier densities.

Identification of distinct electronic regions: narrow interface, intermediate zones, and bulk-like areas.

Abstract

Low dimensionality, broken symmetry and easily-modulated carrier concentrations provoke novel electronic phase emergence at oxide interfaces. However, the spatial extent of such reconstructions - i.e. the interfacial "depth" - remains unclear. Examining LaAlO$_3$/SrTiO$_3$ heterostructures at previously unexplored carrier densities $n_{2D}\geq6.9\times10^{14}$ cm$^{-2}$, we observe a Shubnikov-de Haas effect for small in-plane fields, characteristic of an anisotropic 3D Fermi surface with preferential $d_{xz,yz}$ orbital occupancy extending over at least 100~nm perpendicular to the interface. Quantum oscillations from the 3D Fermi surface of bulk doped SrTiO$_3$ emerge simultaneously at higher $n_{2D}$. We distinguish three areas in doped perovskite heterostructures: narrow ($<20$ nm) 2D interfaces housing superconductivity and/or other emergent phases, electronically isotropic regions far ($>120$ nm) from the interface and new intermediate zones where interfacial proximity renormalises the electronic structure relative to the bulk.