Multiple Superconducting Phases in Rhombohedral Heptalayer Graphene

TL;DR

This study reports the discovery of superconductivity in rhombohedral heptalayer graphene, revealing how layer number and electronic structure influence superconducting phases in multilayer graphene systems.

Contribution

First observation of superconductivity in moiré-free rhombohedral heptalayer graphene, showing unique magnetic responses and electronic origins compared to other multilayer graphene.

Findings

Superconductivity appears at low electric displacement fields

Distinct magnetic responses compared to pentalayer graphene

Superconductivity arises from a half-metallic normal state

Abstract

Crystalline rhombohedral multilayer graphene (RMG) has emerged as an ideal platform for studying unconventional superconductivity. Here, we report the observation of superconductivity in moir\'eless rhombohedral heptalayer graphene (RHG) at zero magnetic field. The superconducting phases emerge at low displacement electric fields (|D| < 0.2 V/nm) and are symmetrically distributed about D = 0, with one robust state exhibiting zero resistance and two weaker superconducting features. Comparisons with rhombohedral pentalayer graphene (RPG) reveal distinct perpendicular magnetic-field responses, and quantum oscillation measurements indicate that superconductivity in RHG arises from a half-metallic normal state. These results highlight the strong dependence of superconductivity on layer number and electronic structure in RMG systems and provide new insights into its microscopic origin.