Посилання:Manifestation of the Upper Hubbard band in the 2D Hubbard model at low electron density / M.Yu. Kagan, V.V. Val’kov, P. Woelfle // Физика низких температур. — 2011. — Т. 37, № 9-10. — С. 1046–1052. — Бібліогр.: 16 назв. — англ.
Підтримка:We acknowledge helpful discussions with P.B. Wiegman, D. Vollhardt, P. Fulde, K.I. Kugel, and A.F. Barabanov.
This work was supported by RFBR grants №11-02-00798 and 11-02-00741.
We consider the 2D Hubbard model in the strong-coupling case (U >> W) and at low electron density (nd² << 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.