Fermi lune and transdimensional orbital magnetism in rhombohedral multilayer graphene

TL;DR

This paper reports the discovery of a novel low-symmetry Fermi surface called 'Fermi lune' in rhombohedral multilayer graphene, leading to unique transport phenomena and a new type of magnetism driven by electron interactions.

Contribution

It introduces the Fermi lune structure, demonstrating its role in symmetry breaking, non-reciprocal transport, and transdimensional orbital magnetism in multilayer graphene.

Findings

Fermi lune has crescent-shaped energy contours.

Spontaneous symmetry breaking leads to giant non-reciprocity.

Coupling with superlattice yields a Chern insulator with quantized Hall effect.

Abstract

The symmetry and geometry of the Fermi surface play an essential role in governing the transport properties of a metallic system. A Fermi surface with reduced symmetry is intimately tied to unusual transport properties such as anomalous Hall effect and nonlinear Hall effect. Here, combining theoretical calculations and transport measurements, we report the discovery of a new class of bulk Fermi surface structure with unprecedented low symmetry, the ``Fermi lune", with peculiar crescent shaped Fermi energy contours, in rhombohedral multilayer graphene. This emergent Fermi-lune structure driven by electron-electron interactions spontaneously breaks time-reversal, mirror, and rotational symmetries, leading to two distinctive phenomena: giant intrinsic non-reciprocity in longitudinal transport and a new type of magnetism termed ``transdimensional orbital magnetism". Coupling the Fermi lune to a superlattice potential further produces a novel Chern insulator exhibiting quantized anomalous Hall effect controlled by in-plane magnetic field. Our work unveils a new symmetry breaking state of matter in the transdimensional regime, which opens an avenue for exploring correlated and topological quantum phenomena in symmetry breaking phases.