Parallel electron-hole bilayer conductivity from electronic interface reconstruction

TL;DR

This study combines first principles calculations and experiments to show that a SrTiO$_3$ capping layer on LaAlO$_3$/SrTiO$_3$ interfaces induces early electronic reconstruction, revealing two closely spaced electron and hole conducting sheets.

Contribution

It demonstrates that a SrTiO$_3$ capping layer lowers the LaAlO$_3$ thickness needed for electronic reconstruction and uncovers spatially separated electron-hole sheets at the interface.

Findings

Capping layer prevents surface reconstruction.

Electronic reconstruction occurs at lower LaAlO$_3$ thickness.

Two spatially separated electron and hole sheets are observed.

Abstract

The perovskite SrTiO$_3$-LaAlO$_3$ structure has advanced to a model system to investigate the rich electronic phenomena arising at polar interfaces. Using first principles calculations and transport measurements we demonstrate that an additional SrTiO$_3$ capping layer prevents structural and chemical reconstruction at the LaAlO$_3$ surface and triggers the electronic reconstruction at a significantly lower LaAlO$_3$ film thickness than for the uncapped systems. Combined theoretical and experimental evidence (from magnetotransport and ultraviolet photoelectron spectroscopy) suggests two spatially separated sheets with electron and hole carriers, that are as close as 1 nm.