Rigorous derivation of the mean-field Green functions of the two-band Hubbard model of superconductivity
The Green function (GF) equation of motion technique for solving the effective two-band Hubbard model of high-Tc superconductivity in cuprates (Plakida et al 1995 Phys. Rev. B 51 16599, Plakida et al 2003 JETP 97 331) rests on the Hubbard operator (HO) algebra. We show that, if we take into account the invariance to translations and spin reversal, the HO algebra results in invariance properties of several specific correlation functions. The use of these properties allows rigorous derivation and simplification of the expressions of the frequency matrix (FM) and of the generalized mean-field approximation (GMFA) Green functions (GFs) of the model. For the normal singlet-hopping and anomalous exchange pairing correlation functions which enter the FM and GMFA-GFs, an approximation procedure based on the identification and elimination of exponentially small quantities is described. It secures the reduction of the correlation order to GMFA-GF expressions.
Journal of Physics A Mathematical General
- Pub Date:
- September 2007
- Condensed Matter - Superconductivity;
- Condensed Matter - Strongly Correlated Electrons
- 16 pages, Submitted to J. Phys. A: Mathematical and Theoretical