Hydrostatic pressure response of an oxide two-dimensional electron system

TL;DR

This study investigates how hydrostatic pressure influences the properties of oxide-based 2D electron systems, revealing a reversible doubling of carrier density and associated changes in conductivity and mobility at LaAlO3-SrTiO3 interfaces.

Contribution

It provides the first detailed experimental and theoretical analysis of the pressure response of oxide 2D electron systems, highlighting their high tunability and underlying mechanisms.

Findings

Pressure of ~2 GPa doubles the 2D carrier density at 4 K.

Conductivity and mobility decrease under applied pressure.

First-principles simulations support the experimental observations.

Abstract

Two-dimensional electron systems with fascinating properties exist in multilayers of standard semiconductors, on helium surfaces, and in oxides. Compared to the two-dimensional (2D) electron gases of semiconductors, the 2D electron systems in oxides are typically more strongly correlated and more sensitive to the microscopic structure of the hosting lattice. This sensitivity suggests that the oxide 2D systems are highly tunable by hydrostatic pressure. Here we explore the effects of hydrostatic pressure on the well-characterized 2D electron system formed at LaAlO$_{3}$ -SrTiO$_{3}$ interfaces[1] and measure a pronounced, unexpected response. Pressure of $\sim$2 GPa reversibly doubles the 2D carrier density $n_{s}$ at 4 K. Along with the increase of $n_{s}$, the conductivity and mobility are reduced under pressure. First-principles pressure simulations reveal the same behavior of the carrier density and suggest a possible mechanism of the mobility reduction, based on the dielectric properties of both materials and their variation under external pressure.