Side gate tunable Josephson junctions at the LaAlO$_3$/SrTiO$_3$ interface

TL;DR

This paper demonstrates the fabrication and control of side gate tunable Josephson junctions at the LaAlO$_3$/SrTiO$_3$ interface, enabling precise manipulation of superconducting properties for potential nanoelectronic applications.

Contribution

It introduces a single-step lithographic process to create gate tunable Josephson junctions with side gates, offering a new method for nanoscale control of interface superconductivity.

Findings

Side gates effectively tune normal-state resistance and critical current.

Conductance and Josephson current exhibit mesoscopic fluctuations.

Realization of a superconducting quantum interference device with independently controlled junctions.

Abstract

Novel physical phenomena arising at the interface of complex oxide heterostructures offer exciting opportunities for the development of future electronic devices. Using the prototypical LaAlO$_3$/SrTiO$_3$ interface as a model system, we employ a single-step lithographic process to realize gate tunable Josephson junctions through a combination of lateral confinement and local side gating. The action of the side gates is found to be comparable to that of a local back gate, constituting a robust and efficient way to control the properties of the interface at the nanoscale. We demonstrate that the side gates enable reliable tuning of both the normal-state resistance and the critical (Josephson) current of the constrictions. The conductance and Josephson current show mesoscopic fluctuations as a function of the applied side gate voltage, and the analysis of their amplitude enables the extraction of the phase coherence and thermal lengths. Finally, we realize a superconducting quantum interference device in which the critical currents of each of the constriction-type Josephson junctions can be controlled independently via the side gates.