Pair density wave in quarter metals from a repulsive fermionic interaction in graphene heterostructures: A renormalization group study

Abstract

Electronic bands in chirally stacked $n$ layer carbon-based honeycomb heterostructures, encompassing rhombohedral or ABC ($n \geq 3$), Bernal or AB bilayer ($n=2$), and monolayer ($n=1$) graphene, possess four-fold valley and spin degeneracy. Such systems with $n \geq 2$, when subject to external perpendicular electric displacement fields, feature a fully degenerate metal at high doping, a spin polarized but valley degenerate half-metal at moderate doping, and a non-degenerate quarter metal at low doping. Due to the fully polarized nature of the quasiparticles in the quarter metal, realized around one particular valley otherwise chosen spontaneously, it can sustain a single local superconducting ground state, representing a pair density wave that is chiral and odd parity in nature. From a leading order renormalization group analysis, here we show that repulsive density-density interaction among such polarized fermionic excitations can foster the pair density wave phase at low temperatures. Connections with experimentally observed superconducting states in the close vicinity of the quarter metal in some members of such graphene heterostructures family are discussed and possible routes to realize such a paired state in optical honeycomb lattices are highlighted.