Superconductivity in the vicinity of an isospin-polarized state in a cubic Dirac band

Abstract

We present a theory of superconducting pairing originating from soft critical fluctuations near isospin-polarized states in rhombohedral trilayer graphene. Using a symmetry-based approach, we determine possible isospin order types and derive the effective electron-electron interactions mediated by isospin fluctuations. Superconductitivty arising due to these interactions has symmetry and order parameter structure that depend in a unique way on the "mother" isospin order. This model naturally leads to a superconducting phase adjacent to isospin-ordering phase transition, which mimics the behavior observed in experiment. The symmetry of the paired state predicted for the isospin order type inferred in experiments matches the observations. These findings support a scenario of superconductivity originating from electron-electron interactions.