Absence of long-range superconducting correlations in the frustrated 1/2-filled band Hubbard model

TL;DR

This study uses many-body calculations to investigate superconducting correlations in the half-filled band Hubbard model on large anisotropic triangular lattices, finding no evidence of superconductivity in the thermodynamic limit.

Contribution

It provides comprehensive numerical evidence that the half-filled Hubbard model does not exhibit superconductivity across a wide range of anisotropies, challenging its applicability to certain organic superconductors.

Findings

Superconducting correlations decrease with increasing U.

Correlations approach noninteracting electron behavior at large lattices.

No superconductivity observed in the thermodynamic limit.

Abstract

We present many-body calculations of superconducting pair-pair correlations in the ground state of the half-filled band Hubbard model on large anisotropic triangular lattices. Our calculations cover nearly the complete range of anisotropies between the square and isotropic triangular lattice limits. We find that the superconducting pair-pair correlations decrease monotonically with increasing onsite Hubbard interaction U for inter-pair distances greater than nearest neighbor. For the large lattices of interest here the distance dependence of the correlations approaches that for noninteracting electrons. Both these results are consistent with the absence of superconductivity in this model in the thermodynamic limit. We conclude that the effective 1/2-filled band Hubbard model, suggested by many authors to be appropriate for the kappa-(BEDT-TTF)-based organic charge-transfer solids, does not explain the superconducting transition in these materials.