Mean Field Theory of RVB and Superconductivity

Abstract

The mean field theory for the coupled fermion (spinon)-boson (holon) system is developed by taking account self-consistently of coherent motions of both spinon and holon and singlet pair of spinon (RVB). The relative phase of RVB order parameters in x - and , y -directions, whose magnitudes are fixed to be the same, is treated as arbitrary. The phase, which minimizes the free energy, is found to be π for wide range of parameters. The bose condensation of holons is also examined in the case of weak interlayer electron transfer integrals. The specific heat, magnetic susceptibility and nuclear relaxation rate are calculated. It is found that their anomalies at the superconducting transition temperature depend markedly on the concentration of holons. The T -linear term in specific heat at low temperatures is shown to be vanishing, which is consistent with the recent experiments in Bi-Sr-Ca-Cu-O by Sera et al . and Kumagai et al .