# Superconductivity of strongly correlated electrons on the honeycomb lattice

## TL;DR

This paper develops a microscopic theory for superconductivity in the t-J model on a honeycomb lattice, revealing d + id'-pairing mediated by antiferromagnetic exchange and exploring the effects of doping and magnetic order.

## Contribution

It introduces a detailed Green function approach for the t-J model on the honeycomb lattice, identifying the pairing symmetry and doping dependence of superconductivity.

## Key findings

- Superconductivity with d + id'-pairing mediated by antiferromagnetic exchange.
- Two-peak structure of Tc related to van Hove singularities.
- Possible coexistence of antiferromagnetism and superconductivity at small doping.

## Abstract

A microscopic theory of the electronic spectrum and of superconductivity within the t-J model on the honeycomb lattice is developed. We derive the equations for the normal and anomalous Green functions in terms of the Hubbard operators by applying the projection technique. Superconducting pairing of d + id'-type mediated by the antiferromagnetic exchange is found. The superconducting Tc as a function of hole doping exhibits a two-peak structure related to the van Hove singularities of the density of states for the two-band t-J model. At half-filling and for large enough values of the exchange coupling, gapless superconductivity may occur. For small doping the coexistence of antiferromagnetic order and superconductivity is suggested. It is shown that the s-wave pairing is prohibited, since it violates the constraint of no-double-occupancy.