Orientational tuning of the Fermi sea of confined electrons at the SrTiO3 (110) and (111) surfaces

TL;DR

This study reveals how the electronic structure of confined electrons at SrTiO3 surfaces varies with crystallographic orientation, affecting properties like Fermi surfaces and orbital ordering, with implications for designing novel 2D electronic states.

Contribution

It demonstrates the orientational dependence of the electronic states at SrTiO3 surfaces using ARPES, highlighting the influence of crystallographic symmetry and effective mass on electronic properties.

Findings

Distinct Fermi surfaces for (110), (111), and (001) surfaces

Similar carrier concentration and thickness across orientations

Surface orientation affects orbital ordering and subband masses

Abstract

We report the existence of confined electronic states at the (110) and (111) surfaces of SrTiO3. Using angle-resolved photoemission spectroscopy, we find that the corresponding Fermi surfaces, subband masses, and orbital ordering are different from the ones at the (001) surface of SrTiO3. This occurs because the crystallographic symmetries of the surface and sub-surface planes, and the electron effective masses along the confinement direction, influence the symmetry of the electronic structure and the orbital ordering of the t2g manifold. Remarkably, our analysis of the data also reveals that the carrier concentration and thickness are similar for all three surface orientations, despite their different polarities. The orientational tuning of the microscopic properties of two-dimensional electron states at the surface of SrTiO3 echoes the tailoring of macroscopic (e.g. transport) properties reported recently in LaAlO3/SrTiO3 (110) and (111) interfaces, and is promising for searching new types of 2D electronic states in correlated-electron oxides.