Impact of Spin-Orbit Coupling on Superconductivity in Rhombohedral Graphene

TL;DR

This study investigates how spin-orbit coupling affects superconductivity in rhombohedral trilayer graphene, revealing new superconducting states and phases, with findings that challenge previous expectations about SOC's effects.

Contribution

It provides the first detailed transport measurements of TMD-proximitized RTG, discovering new superconducting and metallic phases, and showing SOC's unexpected suppression of existing superconductivity.

Findings

Discovery of a new hole-doped superconducting state SC4 with Tc = 230 mK

Identification of a three-quarter-metal (TQM) phase breaking isospin symmetry

Observation that SOC suppresses the original superconducting state SC1 in RTG

Abstract

Spin-orbit coupling (SOC) has played an important role in many topological and correlated electron materials. In graphene-based systems, SOC induced by transition metal dichalcogenide (TMD) at proximity was shown to drive topological states and strengthen superconductivity. However, in rhombohedral multilayer graphene, a robust platform for electron correlation and topology, superconductivity and the role of SOC remain largely unexplored. Here we report transport measurements of TMD-proximitized rhombohedral trilayer graphene (RTG). We observed a new hole-doped superconducting state SC4 with Tc = 230 mK. On the electron-doped side, we identified a new isospin-symmetry breaking three-quarter-metal (TQM) phase and observed the nearby weak superconducting state SC3 is significantly enhanced. Surprisingly, the original superconducting state SC1 in bare RTG is strongly suppressed in the presence of TMD - opposite to the effect of SOC on all other graphene superconductivities. Our observations form the basis of exploring superconductivity and non-Abelian quasiparticles in rhombohedral graphene devices.