Quantum Monte Carlo study of the pairing correlation in the Hubbard ladder

TL;DR

This study uses Quantum Monte Carlo simulations to investigate singlet pairing correlations in the Hubbard ladder, revealing finite-size effects influence the observed correlations and suggesting conditions for enhanced pairing.

Contribution

It demonstrates how finite-size effects impact pairing correlations in Hubbard ladders and identifies conditions that mimic the thermodynamic limit for better understanding.

Findings

Enhanced pairing correlations are observed when energy levels of bonding and anti-bonding bands are close.

Finite systems' energy level discreteness significantly affects pairing correlation measurements.

Results support the possibility of slow decay of pairing correlations under specific conditions.

Abstract

An extensive Quantum Monte Carlo calculation is performed for the two-leg Hubbard ladder model to clarify whether the singlet pairing correlation decays slowly, which is predicted from the weak-coupling theory but controversial from numerical studies. Our result suggests that the discreteness of energy levels in finite systems affects the correlation enormously, where the enhanced pairing correlation is indeed detected if we make the energy levels of the bonding and anti-bonding bands lie close to each other at the Fermi level to mimic the thermodynamic limit.