Dominant mobility modulation by the electric field effect at the LaAlO_3 / SrTiO_3 interface

TL;DR

This study reveals that electric field modulation at the LaAlO_3 / SrTiO_3 interface primarily affects electron mobility rather than carrier density, significantly impacting superconductivity and disorder strength.

Contribution

It demonstrates that electric field effects predominantly modulate mobility over carrier density at the interface, providing new insights into the superconductor-insulator transition mechanisms.

Findings

Mobility variation is nearly five times larger than sheet carrier density change.

Superconductivity can be suppressed by both positive and negative gate biases.

Disorder strength increases significantly across the superconductor-insulator transition.

Abstract

Caviglia et al. [Nature (London) 456, 624 (2008)] have found that the superconducting LaAlO_3 / SrTiO_3 interface can be gate modulated. A central issue is to determine the principal effect of the applied electric field. Using magnetotransport studies of a gated structure, we find that the mobility variation is almost five times as large as the sheet carrier density. Furthermore, superconductivity can be suppressed at both positive and negative gate bias. These results indicate that the relative disorder strength strongly increases across the superconductor-insulator transition.