Evolution of pairing from weak to strong coupling on a honeycomb lattice

TL;DR

This paper investigates how electron pairing evolves from weak to strong coupling on a honeycomb lattice, revealing a BCS-BEC crossover through quantum Monte Carlo simulations and various physical observables.

Contribution

It provides numerical evidence of the BCS-BEC crossover on a honeycomb lattice with a small Fermi surface, highlighting similarities and differences with extended Fermi surface systems.

Findings

Evidence of BCS-BEC crossover with increasing coupling

No significant qualitative difference in crossover compared to extended Fermi surface systems

Distinct behavior observed at weak coupling in the BCS regime

Abstract

We study the evolution of the pairing from weak to strong coupling on a honeycomb lattice by Quantum Monte Carlo. We show numerical evidence of the BCS-BEC crossover as the coupling strength increases on a honeycomb lattice with small fermi surface by measuring a wide range of observables: double occupancy, spin susceptibility, local pair correlation, and kinetic energy. Although at low energy, the model sustains Dirac fermions, we do not find significant qualitative difference in the BCS-BEC crossover as compared to those with an extended Fermi surface, except at weak coupling, BCS regime.