DENSITY OF STATES AND TRANSPORT PROPERTIES IN NORMAL STATE OF CUPRATE-SUPERCONDUCTORS

Abstract

Three-state model for quasi-two dimensional Cu-O layer of oxide superconductor is considered. The density of states and transport properties (resistivity and thermo-electric power) in normal state are calculated for resonance and non-resonance condition of Cu d-level and O p-level. Thermoelectric power can be positive or negative depending on carrier concentration, bare charge transfer gap and transfer integral between d–p and p–p states and its sign changes at higher temperature. The thermo-electric power when positive passes through a maximum with increase in temperature. The value at its maximum and its location moves up with decrease in carrier concentration. The thermal variation of resistivity changes from metallic like (linear in -T) to semiconducting-like as carrier concentration reduces by small amount.