Hole pairs in the two-dimensional Hubbard model

Abstract

The interactions between holes in the Hubbard model, in the low density, intermediate to strong coupling limit, are investigated. 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. Our results are derived by systematically improving mean field calculations. The method can also be used to derive known properties of isolated spin polarons.PACS number(s): 02.70.Lq, 71.10.Fd

Dynamics of holes and universality class of the antiferromagnetic transition in the two-dimensional Hubbard model

“…This is a standard procedure in molecular physics, where Hartree-Fock (HF) solutions are improved by the Configuration Interaction (CI) method. The resulting polaron band is in reasonable agreement with other calculations [17,18].…”

“…Thus the wavefunction |Ψ i is obtained from |Ψ 0 by adding a given number of electron-hole excitations, plus an electron (hole) at site i. As discussed elsewhere [17,18], corrections to this inhomogeneous HF solution can be of two types: low amplitude fluctuations, which can be studied within the RPA [28], and hybridization of solutions centered at different lattice sites [16]. The combination of these solutions leads to wavefunctions of the type |Ψ k = i e i k ri |Ψ i , and to the formation of a polaron band, whose width scales as t 2 /U in the limit of large U .…”

Configuration-interaction approach to hole pairing in the two-dimensional Hubbard model

“…The combination of these effects is an attractive interaction at intermediate values of U/t. The purpose of this work is to discuss in detail the results and the approach proposed in [17]. We present new results which support the validity of our approach, highlighting the physically appealing picture of pairing that it provides.…”

“…We have recently analyzed the dynamics of spin polarons [15,16] and the interactions between them [17] by means of a systematic expansion around mean field calculations of the Hubbard model. Two spin polarons in neighboring sites experience an increase in their internal kinetic energy, due to the overlap of the charge cloud.…”