Absence of Giant Spin Splitting in the Two-Dimensional Electron Liquid at the Surface of SrTiO$_3$ (001)

TL;DR

This study reexamines claims of giant spin splitting at SrTiO$_3$ surfaces and finds no evidence for it, instead supporting a smaller Rashba-like splitting consistent with band calculations.

Contribution

The paper provides experimental evidence against the existence of giant spin splitting at SrTiO$_3$ surfaces, clarifying previous conflicting reports.

Findings

No detectable spin polarization in photoemission experiments.

Results exclude the presence of giant spin splitting.

Supports Rashba-like splitting consistent with theoretical calculations.

Abstract

We reinvestigate the putative giant spin splitting at the surface of SrTiO$_3$ reported by Santander-Syro $et~al.$ [Nature Mat. 13, 1085 (2014)]. Our spin- and angle-resolved photoemission experiments on (001) oriented surfaces supporting a two-dimensional electron liquid with high carrier density show no detectable spin polarization in the photocurrent. We demonstrate that this result excludes a giant spin splitting while it is fully consistent with the unconventional Rashba-like splitting seen in band structure calculations that reproduce the experimentally observed ladder of quantum confined subbands.