Coupling between tilts and charge carriers at polar-nonpolar perovskite interfaces

TL;DR

This paper develops a theoretical framework that couples tilts and charge carriers at polar-nonpolar perovskite interfaces, enhancing understanding of phase transitions and interface phenomena with potential for controlled electronic properties.

Contribution

It introduces a Landau-Ginzburg theory incorporating tilt-charge coupling and electric field effects, extending previous models of polar instability at perovskite interfaces.

Findings

Coupling significantly enriches the physics of metal-insulator transitions.

Model predicts scenarios with one or two phase transitions, continuous or discontinuous.

First-principles calculations estimate parameters for LaAlO3/SrTiO3 interfaces.

Abstract

The phenomenological theory for the polar instability giving rise to a two-dimensional electron gas at perovskite interfaces is hereby extended to include the coupling to perovskite tilts. A Landau theory for homogeneous tilts is first explored, setting the scene for the further, more realistic Landau-Ginzburg theory describing varying tilt amplitudes across a thin film. The theory is also generalized to account for the response to an applied electric field normal to the interface, which allows a finer control on phase transitions. The conventionally described physics of a single metal-insulator transition is substantially enriched by the coupling, the model describing various scenarios with one or two transitions, possibly continuous or discontinuous. First-principles calculations permit the estimation of the parameters defining the model, which have been calculated for the interface between lanthanum aluminate and strontium titanate.