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 givenby ΣPG(iωn) = −EG2(k) G0(k,−iωn),where G0(k,iωn) is the one-particle free Green function. Going beyond this mean-field model forthe pseudogap we now take into account fluctuations of the pseudogap asΣPG(iωn) = −EG2(k) GPG(k,−iωn),where GPG(k,iωn) is the pseudogap one-particle Green function and is the value of the pseudogap parameter. We study the combined effect ofα′, the second-nearest neighbour in the band structure () and the cutoff frequency, ωD, on the superconducting critical temperature,Tc, as a function of the number of carriers per site,n. The effectof V/t andωD/t is to increasethe value of Tc/t, while α′ displaces Tc,max/t away from half-filling.