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Fermi‐liquid quasi‐particles and d x 2 ‐y 2 ‐superconductivity in the two‐dimensional Hubbard model
Author(s) -
Wermbter S.
Publication year - 1998
Publication title -
annalen der physik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.009
H-Index - 68
eISSN - 1521-3889
pISSN - 0003-3804
DOI - 10.1002/andp.2060070104
Subject(s) - physics , fermi liquid theory , condensed matter physics , fermi surface , superconductivity , momentum (technical analysis) , hubbard model , fermi gamma ray space telescope , fermi level , phase diagram , phase (matter) , quantum mechanics , electron , finance , economics
A frequency‐ and momentum‐renormalization‐group acceleration together with an analytical approach is used to obtain the retarded Green's function in the self‐consistent and conserving fluctuation‐exchange (FLEX) approximation for the two‐dimensional Hubbard model in the normal state and in the superconducting state. The analytical expressions for this approach are given. For band‐fillings near half filling the self‐energy in the normal state exhibits Fermi‐liquid behaviour for low temperatures and frequencies near the chemical potential, if the momentum is chosen near the Fermi‐surface. However due to the presence of large many body effects the observed Fermi‐liquid region near the chemical potential and near the Fermi‐surface is very small. Results for the single particle density of states, the occupation number and the spectral function are presented. The superconducting state with d x 2 ‐y 2symmetry is obtained for U = 2 to U = 6 and a ( U,n )‐phase diagram for the transition temperature T c is presented. A maximum T c /t of 0.0275 is obtained for U = 6 near half filling.