A d-wave pseudogap model beyond BCS for the cuprates

Abstract

One of the most intriguing aspects of high-temperature superconductors is the presence of the pseudogap in the normal and the superconducting phases of the cuprate compounds. Several pseudogap models have been proposed to explain the abnormal properties of the cuprates. One of the recent models (J.J. Rodríguez-Núñez, A.A. Schmidt, H. Beck, J. Phys.: Condens. Matter 17 (2005) 323) relies on the assumption that the self energy is given by ∑ PG ( i ω n ) = - E g 2 ( k ) G 0 ( k ,- i ω n ) , where G 0 ( k , i ω n ) is the one-particle free Green function. Going beyond this mean field model for the pseudogap we now take into account fluctuations of the pseudogap as ∑ PG ( i ω n ) = - E g 2 ( k ) G PG ( k ,- i ω n ) , where G PG ( k , i ω n ) is the one-particle full Green function. We study the combined effect of the band structure and the Debye frequency, ω D , on the superconducting critical temperature, T c , as a function of the number of carriers per site, n.