Spin and Orbital Metallic Magnetism in Rhombohedral Trilayer Graphene

TL;DR

This paper provides a comprehensive theoretical explanation for the metallic broken spin/valley symmetry states in ABC trilayer graphene under a transverse displacement field, emphasizing momentum-space condensation and Fermi surface reconstructions.

Contribution

It introduces a new theoretical framework combining electronic structure models and mean field theory to interpret experimental magneto-oscillation data in ABC trilayer graphene.

Findings

Identification of large outer Fermi surfaces with majority-flavor states.

Discovery of small inner hole-like Fermi surfaces responsible for nematic order.

Explanation of quantum oscillation frequency fractionalization phenomena.

Abstract

We provide a complete theoretical interpretation of the metallic broken spin/valley symmetry states recently discovered in ABC trilayer graphene (ABC) perturbed by a large transverse displacement field. Our conclusions combine insights from ABC trilayer graphene electronic structure models and mean field theory, and are guided by precise magneto-oscillation Fermi-surface-area measurements. We conclude that the physics of ABC trilayer graphene is shaped by the principle of momentum-space condensation, which favors Fermi surface reconstructions enabled by broken spin/valley flavor symmetries when the single-particle bands imply thin annular Fermi seas. We find one large outer Fermi surface enclosed majority-flavor states and one or more small inner hole-like Fermi surfaces enclosed minority-flavor states that are primarily responsible for nematic order. The smaller surfaces can rotate along a ring of van-Hove singularities or reconstruct into multiple Fermi surfaces with little cost in energy. We propose that the latter property is responsible for the quantum oscillation frequency fractionalization seen experimentally in some regions of the carrier-density/displacement-field phase diagram.