Electrostatic control of quantum phases in KTaO3-based planar constrictions

TL;DR

This paper presents a scalable method to create and control quantum phases in KTaO3-based heterostructures using electrostatic gating, enabling tunable superconductivity and Coulomb blockade effects in nanoscale constrictions.

Contribution

It introduces a novel fabrication technique for tunable quantum nanostructures in complex oxides using high dielectric permittivity for electrostatic control.

Findings

Effective modulation of superconducting properties with low gate voltage.

Observation of Coulomb blockade patterns in the constrictions.

Scalable and versatile fabrication process for oxide-based quantum devices.

Abstract

Two-dimensional electron gases (2DEGs) formed at complex oxide interfaces offer a unique platform to engineer quantum nanostructures. However, scalable fabrication of locally addressable devices in these materials remains challenging. Here, we demonstrate an efficient fabrication approach by patterning narrow constrictions in a superconducting KTaO3-based heterostructure. The constrictions are individually tunable via the coplanar side gates formed within the same 2DEG plane. Our technique leverages the high dielectric permittivity of KTaO3 (epsilon_r ~ 5000) to achieve strong electrostatic modulation of the superconducting 2DEG. Transport measurements through the constriction reveal a range of transport regimes: Within the superconducting state, we demonstrate efficient modulation of the critical current and Berezinskii Kosterlitz Thouless (BKT) transition temperature at the weak link. Further tuning of the gate voltage reveals an unexpectedly regular Coulomb blockade pattern. All of these states are achievable with a side gate voltage |V_SG| < 1 V. The fabrication process is scalable and versatile, enabling a platform both to make superconducting field-effect transistors and to study a wide array of physical phenomena present at complex oxide interfaces.