Large tunable kinetic inductance in a twisted graphene superconductor

TL;DR

This paper demonstrates large, tunable kinetic inductance in twisted trilayer graphene superconductors integrated into SQUIDs, revealing potential for graphene-based tunable superconducting circuit elements.

Contribution

It introduces a method to measure and control kinetic inductance in twisted graphene superconductors, linking it to coherence length and enabling tunable superconducting circuit components.

Findings

Kinetic inductance up to 150 nH per square observed.

Kinetic inductance and critical current density are universally related.

Upper bound of superconducting coherence length is approximately 200 nm.

Abstract

Twisted graphene based moir\'e heterostructures host a flat band at the magic angles where the kinetic energy of the charge carriers is quenched and interaction effects dominate. This results in emergent phases such as superconductors and correlated insulators that are electrostatically tunable. We investigate superconductivity in twisted trilayer graphene (TTG) by integrating it as the weak link in a superconducting quantum interference device (SQUID). The measured current phase relation (CPR) yields a large and tunable kinetic inductance, up to 150 nH per square, of the electron and hole type intrinsic superconductors. We further show that the specific kinetic inductance and the critical current density are universally related via the superconducting coherence length, and extract an upper bound of 200 nm for the coherence length. Our work opens avenues for using graphene-based superconductors as tunable elements in superconducting circuits.