Single spin-polarised Fermi surface in SrTiO$_3$ thin films

TL;DR

This study demonstrates control over the band filling in SrTiO$_3$ thin films, revealing a single spin-polarised 2D Fermi surface, which could be useful for Majorana physics and quantum applications.

Contribution

It shows that the 2DEG in SrTiO$_3$ thin films can be tuned to produce a single spin-polarised Fermi surface using angle-resolved photoemission spectroscopy.

Findings

The 2DEG does not extend beyond 2 unit cells into the film.

The properties depend on surface SrO$_x$ and dielectric response.

A single spin-polarised Fermi surface was observed.

Abstract

The 2D electron gas (2DEG) formed at the surface of SrTiO$_3$(001) has attracted great interest because of its fascinating physical properties and potential as a novel electronic platform, but up to now has eluded a comprehensible way to tune its properties. Using angle-resolved photoemission spectroscopy with and without spin detection we here show that the band filling can be controlled by growing thin SrTiO$_3$ films on Nb doped SrTiO$_3$(001) substrates. This results in a single spin-polarised 2D Fermi surface, which bears potential as platform for Majorana physics. Based on our results it can furthermore be concluded that the 2DEG does not extend more than 2 unit cells into the film and that its properties depend on the amount of SrO$_x$ at the surface and possibly the dielectric response of the system.