Anisotropic electrical resistance in mesoscopic LaAlO$_3$/SrTiO$_3$ devices with individual domain walls

TL;DR

This study investigates how structural domain walls in SrTiO$_3$ influence anisotropic electrical resistance in mesoscopic LaAlO$_3$/SrTiO$_3$ devices, revealing significant directional dependence of electron conduction related to domain wall orientation.

Contribution

It provides the first detailed characterization of anisotropic electron conduction related to individual domain walls in mesoscopic LAO/STO devices across a wide temperature range.

Findings

Resistance is higher when current is parallel to the domain wall.

Maximum resistance ratio observed is at least 10, up to 10^5 at 10K.

Electronic anisotropy linked to domain wall orientation affects conduction.

Abstract

The crystal structure of bulk SrTiO$_3$(STO) transitions from cubic to tetragonal at around 105K. Recent local scanning probe measurements of LaAlO$_3$/SrTiO$_3$ (LAO/STO) interfaces indicated the existence of spatially inhomogeneous electrical current paths and electrostatic potential associated with the structural domain formation in the tetragonal phase of STO. However, how these effects impact the electron conduction in LAO/STO devices has not been fully studied. Here we report a study of temperature dependent electronic transport in combination with the polarized light microscopy of structural domains in mesoscopic scale LAO/STO devices. By reducing the spatial size of the conductive interface to be comparable to the size of a single tetragonal domain of STO, the anisotropy of interfacial electron conduction in relationship to the domain wall and its direction was characterized in the temperature range $T$=10-300K. It was found that the four-point resistance measured with current parallel to the domain wall in device is larger than the resistance measured perpendicular to the domain wall. This observation is qualitatively consistent with the current diverting effect from a more conductive domain wall within the sample. Among all the samples studied, the maximum resistance ratio found is at least 10 and could be as large as 10$^5$ at $T$=10K. This electronic anisotropy may have implications on other oxide hetero-interfaces and the further understanding of electronic/magnetic phenomena found in LAO/STO.