Chiral superconductivity from repulsive interactions in doped graphene

TL;DR

This paper predicts that doped graphene can host chiral d+id superconductivity driven by repulsive interactions, with enhanced critical temperature at a specific doping level due to a singular density of states.

Contribution

It demonstrates that graphene at a particular doping level can exhibit chiral superconductivity from repulsive interactions, using renormalization group analysis and mean field calculations.

Findings

Superconductivity dominates over other orders at the singular doping level.

Superconductivity is of a chiral d+id type, breaking time reversal symmetry.

Enhanced critical temperature T_c occurs due to a singular density of states.

Abstract

We identify graphene as a system where chiral superconductivity can be realized. Chiral superconductivity involves a pairing gap that winds in phase around the Fermi surface, breaking time reversal symmetry. We consider a unique situation arising in graphene at a specific level of doping, where the density of states is singular, strongly enhancing the critical temperature T_c. At this doping level, the Fermi surface is nested, allowing superconductivity to emerge from repulsive electron-electron interactions. We show using a renormalization group method that superconductivity dominates over all competing orders for any choice of weak repulsive interactions. Superconductivity develops in a doubly degenerate, spin singlet channel, and a mean field calculation indicates that the superconductivity is of a chiral d+id type. We therefore predict that doped graphene can provide experimental realization of spin-singlet chiral superconductivity.