Observation of zero-field transverse resistance in AlO$_x$/SrTiO$_3$ interface devices

TL;DR

This study reports the discovery of a zero-field transverse resistance in AlO$_x$/SrTiO$_3$ interface devices, linked to domain wall configurations and their temperature-dependent polarization, revealing new insights into interface transport phenomena.

Contribution

It introduces the observation of zero-field transverse resistance in AlO$_x$/SrTiO$_3$ interfaces and links it to domain wall effects and dielectric properties, a novel finding in oxide heterostructures.

Findings

Transverse resistance appears below ~70 K and grows below ~40 K.

Resistance varies with temperature, gate voltage, and position, and can change sign.

Larger transverse resistance observed in (111) oriented heterostructures.

Abstract

Domain walls in AlO$_x$/SrTiO$_3$ (ALO/STO) interface devices at low temperatures give a rise to a new signature in the electrical transport of two-dimensional carrier gases formed at the surfaces or interfaces of STO-based heterostructures: a finite transverse resistance observed in Hall bars in zero external magnetic field. This transverse resistance depends on the local domain wall configuration and hence changes with temperature, gate voltage, thermal cycling and position along the sample, and can even change sign as a function of these parameters. The transverse resistance is observed below $\simeq$ 70 K but grows and changes significantly below $\simeq$40 K, the temperature at which the domain walls become increasingly polar. Surprisingly, the transverse resistance is much larger in (111) oriented heterostructures in comparison to (001) oriented heterostructures. Measurements of the capacitance between the conducting interface and an electrode applied to the substrate, which reflect the dielectric constant of the STO, indicate that this difference may be related to the greater variation of the temperature dependent dielectric constant with electric field when the electric field is applied in the [111] direction. The finite transverse resistance can be explained inhomogeneous current flow due to the preferential transport of current along domain walls that are not collinear with the nominal direction of the injected current.