Chern number reversal and emergent superconductivity in rhombohedral graphene induced by in-plane magnetic fields

TL;DR

This study explores how in-plane magnetic fields induce Chern number reversal and emergent superconductivity in rhombohedral graphene moire superlattices, revealing new topological and superconducting phases.

Contribution

It demonstrates the control of topological and superconducting states in rhombohedral graphene using in-plane magnetic fields, including Chern number reversal and spin-triplet pairing evidence.

Findings

Observation of Chern number reversal driven by displacement fields and magnetic fields.

Identification of three distinct superconducting phases with different magnetic responses.

Evidence suggesting spin-triplet pairing in field-induced superconductivity.

Abstract

Rhombohedral graphene with topological flat bands offers an ideal platform for realizing correlated and topological quantum phases. Here we investigate hBN aligned eight-layer rhombohedral graphene moire superlattices, which host a robust quantum anomalous Hall (QAH) state alongside three unconventional superconducting phases. For electron-doped carriers away from the moire potential, we observe QAH Chern number reversal driven by the displacement fields and in plane magnetic fields. For hole-doped carriers near the moire superlattice, the three superconducting phases exhibit distinctively different in plane magnetic field responses: one is weakly enhanced, the second is strongly suppressed, and the third exclusively induced by in plane magnetic field. The isotropic in plane magnetic field response in the QAH regime points to interplay between orbital magnetism and spin-orbit coupling, and the field-emergent superconductivity provides compelling evidence for spin-triplet pairing. Our work demonstrates a highly versatile platform for coexisting topological and superconducting states, and highlights in plane magnetic field as a powerful in-situ control knob for engineering novel quantum devices.