Nematic and partially polarized phases in rhombohedral graphene with varying number of layers: An extensive Hartree-Fock Study

TL;DR

This study uses extensive Hartree-Fock calculations to map the phase diagram of rhombohedral graphene with varying layers, revealing diverse correlated phases, nematicity, and symmetry-breaking states influenced by doping and external fields.

Contribution

It provides a comprehensive theoretical phase diagram for multilayer rhombohedral graphene, highlighting the emergence of nematic and polarized phases driven by electron-electron interactions.

Findings

Discovery of cascade of partially-isospin-polarized phases

Identification of nematic states stabilized by interactions

Polarized states stable up to 20 layers

Abstract

Rhombohedral graphene systems with different number of layers feature an abundance of correlated phases and superconducting states in experimental measurements with different doping and displacement fields. Some of the superconducting pockets can emerge from - or close to - one of the correlated states. Therefore, studying the phase diagram of the correlated phases for varying number of layers could be useful to interpret the experimental observations. To achieve this, systematic Hartree-Fock calculations have been performed to build the phase diagram of rhombohedral (ABC-stacked) graphene for different number of layers, in the presence of long-range Coulomb interactions. By varying the external displacement field and carrier density, a cascade of metallic partially-isospin-polarized phases that spontaneously break spin and/or valley (flavor) symmetries is found. In addition, these states can present nematicity, stabilized by electron-electron interactions, exhibiting rich internal complexity. Polarized states are more stable for electron doping, and they are found for systems with up to 20 layers. Moreover, the tunability of the phase diagram via substrate screening and spin-orbit coupling proximity effects has been studied. Our results offer new insights into the role of correlations and symmetry breaking in graphitic systems which will motivate future experimental and theoretical works.