Band Renormalization, Quarter Metals, and Chiral Superconductivity in Rhombohedral Tetralayer Graphene

TL;DR

This paper investigates the role of electron-electron interactions in rhombohedral tetralayer graphene, revealing a novel p-wave, finite-momentum superconducting state that aligns with experimental findings.

Contribution

It introduces a modified Hartree-Fock scheme with internal screening to better predict superconductivity and flavor symmetry breaking in tetralayer graphene.

Findings

Superconductivity arises from spin-valley polarized phases.

The study predicts a p-wave, finite-momentum, time-reversal-symmetry-broken superconducting state.

The formalism reproduces experimental phase diagrams and suggests new exotic phases.

Abstract

Recently, exotic superconductivity emerging from a spin-and-valley-polarized metallic phase has been discovered in rhombohedral tetralayer graphene. To explain this observation, we study the role of electron-electron interactions in driving flavor symmetry breaking, using the Hartree-Fock (HF) approximation, and in stabilizing superconductivity mediated by repulsive interactions. Though mean-field HF correctly predicts the isospin flavors and reproduces the experimental phase diagram, it overestimates the band renormalization near the Fermi energy and suppresses superconducting instabilities. To address this, we introduce a physically motivated scheme that includes internal screening in the HF calculation. Using this formalism, we find superconductivity arising from the spin-valley polarized phase for a range of electric fields and electron dopings. Our findings reproduce the experimental observations and reveal a p-wave, finite-momentum, time-reversal-symmetry-broken superconducting state, encouraging further investigation into exotic phases in graphene multilayers.