Low Temperature Physics: 37, 834 (2011); https://doi.org/10.1063/1.3670026 (6 pages)
Fizika Nizkikh Temperatur: Volume 37, Number 9-10 (September 2011), p. 1046-1052    ( to contents , go back )

Manifestation of the Upper Hubbard band in the 2D Hubbard model at low electron density

M.Yu. Kagan

P.L. Kapitza Institute for Physical Problem, 2 ul. Kosygina, Moscow 119334, Russia
E-mail: kagan@kapitza.ras.ru

V.V. Val’kov

Kirensky Institute of Physics, Akademgorodok, 50, bld. 38, Krasnoyarsk 660036, Russia

P. Woelfle

Institute for Theoretical Condensed Matter physics, Karlsruhe Institute of Technology, Wolfgang-Gaede-Str., 1, Karlsruhe D-76131, Germany
pos Анотація:

Received May 10, 2011

Abstract

We consider the 2D Hubbard model in the strong-coupling case (U >> W) and at low electron density (nd 2 << 1). We find an antibound state as a pole in the two-particle T-matrix. The contribution of this pole in the self-energy reproduces a two-pole structure in the dressed one-particle Green-function similar to the Hubbard-I approximation. We also discuss briefly the Engelbrecht-Randeria mode which corresponds to the pairing of two holes below the bottom of the band for U >> W and low electron density. Both poles produce nontrivial corrections to Landau Fermi-liquid picture already at low electron density but do not destroy it in 2D.

PACS: 71.10.Fd Lattice fermion models (Hubbard model, etc.).

Key words: Hubbard model, Green-function, low electron density.

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