Induced superconductivity in magic-angle twisted trilayer graphene through graphene-metal contacts

TL;DR

This paper investigates how graphene-metal contacts induce and modulate superconductivity in magic-angle twisted trilayer graphene, predicting a maximum transition temperature over 2 K through theoretical modeling of interfacial charge transfer.

Contribution

It provides a theoretical framework for understanding and predicting superconductivity in MATTG when contacted with metals, highlighting the role of work function differences and electric fields.

Findings

Superconductivity forms two domes as a function of work function difference.

Maximum predicted transition temperature exceeds 2 K.

Charge transfer and electric fields are key to inducing superconductivity.

Abstract

Magic-angle twisted trilayer graphene (MATTG) recently exhibited robust superconductivity at a higher transition temperature (TC) than the bilayer version. With electric gating from both the top and bottom sides, the superconductivity was found to be closely associated to two conditions: the finite broken mirror symmetry and carrier concentrations between two to three carriers per moir\'e unite cell. Both conditions may be achieved by graphene-metal contacts where charge transfers and interfacial electric fields are generated to balance work function mismatch. In this study, we explore the superconductivity of MATTG when contacting a metal, through self-consistently solving the interfacial charge transfer with a highly electric-field-dependent band structure of MATTG. The predicted TC of MATTG-metal contacts forms two domes as a function of the work function difference over the interface, with a maximum over 2 K. Our work provides a constructive reference for graphene experiments and industrial applications with graphene-metal and graphene-semiconductor contacts.