Critical temperature for the two-dimensional attractive Hubbard Model

TL;DR

This paper estimates the critical temperature of the 2D attractive Hubbard model using Quantum Monte Carlo simulations, analyzing helicity modulus and pairing correlations to find a higher $T_c$ than previously thought.

Contribution

It provides a new estimate of the critical temperature for the 2D attractive Hubbard model using finite-size scaling and universal jump conditions.

Findings

Critical temperature $T_c$ is higher than previously assumed.

Quantum Monte Carlo simulations up to $18\times 18$ lattices.

Finite-size scaling confirms the robustness of the $T_c$ estimate.

Abstract

The critical temperature for the attractive Hubbard model on a square lattice is determined from the analysis of two independent quantities, the helicity modulus, $\rho_s$, and the pairing correlation function, $P_s$. These quantities have been calculated through Quantum Monte Carlo simulations for lattices up to $18\times 18$, and for several densities, in the intermediate-coupling regime. Imposing the universal-jump condition for an accurately calculated $\rho_s$, together with thorough finite-size scaling analyses (in the spirit of the phenomenological renormalization group) of $P_s$, suggests that $T_c$ is considerably higher than hitherto assumed.