2002/06/28 by V. R. Shaginyan
Physics and Astronomy · #cond-mat.str-el #cond-mat.supr-con
published as Report at NATO ARW, Optical Properties of 2D Systems, St. Petersburg, 2002 · 16 pages, Revtex
arxiv created 2002/06/28 · arxiv updated 2009/11/30
A theory of strongly correlated electron or hole liquids with the fermion condensate is presented and applied to the consideration of quasiparticle excitations in high temperature superconductors, in their superconducting and normal states. This theory describes maximum values of the superconducting gap which can be as big as Δ1∼ 0.1εF, with εF being the Fermi level. We show that the critical temperature 2Tc≃Δ1. If there exists the pseudogap above Tc then 2T^*≃Δ1, and T^* is the temperature at which the pseudogap vanishes. A discontinuity in the specific heat at Tc is calculated. The transition from conventional superconductors to high-Tc ones as a function of the doping level is investigated. The single-particle excitations and their lineshape are also considered. Analyzing experimental data on the high temperature superconductivity in different materials induced by field-effect doping, we show that all these facts can be understood within a theory of the superconductivity based on the fermion condensation quantum phase transition, which can be conceived of as a universal cause of the superconductivity. The main features of room-temperature superconductors are outlined.