# Symmetry and correlation effects on band structure explain the anomalous transport properties of (111) LaAlO$_3$/SrTiO$_3$

## TL;DR

This study explains the anomalous transport properties of the (111) LaAlO₃/SrTiO₃ interface by analyzing symmetry and correlation effects on its band structure, contrasting it with the (001) interface's behavior.

## Contribution

The paper introduces a theoretical model that accounts for symmetry and correlation effects, explaining the distinct transport phenomena observed at the (111) interface.

## Key findings

- (111) interface shows monotonic change in quantum oscillation frequency
- Transport properties at (111) are uncorrelated and nonmonotonic
- Symmetry and correlation effects explain the observed anomalies

## Abstract

The interface between the two insulating oxides SrTiO$_3$ and LaAlO$_3$ gives rise to a two-dimensional electron system with intriguing transport phenomena, including superconductivity, which are controllable by a gate. Previous measurements on the (001) interface have shown that the superconducting critical temperature, the Hall density, and the frequency of quantum oscillations, vary nonmonotonically and in a correlated fashion with the gate voltage. In this paper we experimentally demonstrate that the (111) interface features a qualitatively distinct behavior, in which the frequency of Shubnikov-de Haas oscillations changes monotonically, while the variation of other properties is nonmonotonic albeit uncorrelated. We develop a theoretical model, incorporating the different symmetries of these interfaces as well as electronic-correlation-induced band competition. We show that the latter dominates at (001), leading to similar nonmonotonicity in all observables, while the former is more important at (111), giving rise to highly curved Fermi contours, and accounting for all its anomalous transport measurements.