A pseudogap model beyond BCS for the cuprates: the effect of order parameter symmetry, cutoff frequency and band structure

Abstract

We present an extension of the phenomenological pseudogap model proposed by Rodríguez-Núñez et al (2005 J. Phys.: Condens. Matter 17 323) which relies on the assumption that the self-energy is given by PGwhere G 0 (k, iω 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 aswhere G PG (k, iω n ) is the pseudogap one-particle Green function and E G ( k) is the value of the pseudogap parameter. We study the combined effect of α , the second-nearest neighbour in the band structure ( ( k) = −2t[cos(k x ) + cos(k y )] + 4tα cos(k x ) cos(k y )) and the cutoff frequency, ω D , on the superconducting critical temperature, T c , as a function of the number of carriers per site, n. The effect of V /t and ω D /t is to increase the value of T c /t, while α displaces T c,max /t away from half-filling.