A Configuration Interaction approach to hole pairing in the Two-Dimensional Hubbard Model

TL;DR

This paper uses a Configuration Interaction approach to study hole interactions in the 2D Hubbard model, revealing effective attraction mechanisms at intermediate couplings through improved mean field calculations.

Contribution

It introduces a systematic CI basis set based on local Hartree-Fock configurations, accurately reproducing Heisenberg model properties and analyzing hole pairing in the Hubbard model.

Findings

Dressed spin polarons exhibit increased kinetic energy and hopping rate upon doping.

Effective attraction between holes emerges at intermediate couplings.

The method accurately reproduces properties of the Heisenberg model in the large U limit.

Abstract

The interactions between holes in the Hubbard model, in the low density, intermediate to strong coupling limit, are investigated by systematically improving mean field calculations. The Configuration Interaction basis set is constructed by applying to local Unrestricted Hartree-Fock configurations all lattice translations and rotations. It is shown that this technique reproduces, correctly, the properties of the Heisenberg model, in the limit of large U. Upon doping, dressed spin polarons in neighboring sites have an increased kinetic energy and an enhanced hopping rate. Both effects are of the order of the hopping integral and lead to an effective attraction at intermediate couplings.