The normal state of high temperature oxide superconductor - Pseudogapped metallic state

Looking back on the experiments about the normal state of the high temperat ure superconductor (HTS), the authors point out nine important experimental results. On the basis of these results, the authors have argued that the t wo-dimension, two-subsystem Hamiltonian is the appropriate starting point f or describing the normal state of HTS. By this Hamiltonian, using the decou pling approximation of Green's function method by Kaga through numerical ca lculations, the authors have obtained the temperature dependent pseudogap i n the density of states (DOS), which is consistent qualitatively with the e xperimental results by angle-resolved photoemission spectroscopy (ARPES). T heoretically, this Hamiltonian has the superconducting order parameter of d + s symmetry with d-wave as the main component, which is consistent with e xperiments. Further, the quantum electronic liquid in HTS is a near Fermi l iquid in which there is coexistence of the delocalized states and nearly lo calized states, and there is finite probability for the nearly localized ca rriers to form the nearly localized carrier pairs at any finite temperature .