Investigation of pseudogap and superconducting transitions in hole-doped cuprates

Abstract

We consider the id-density wave (DDW) order, representing the pseudo-gap (PG) state, and the d-wave superconductivity (DSC)within the BCS framework for the two-dimensional (2D) fermion system on a square lattice starting with a mean-field Hamiltonian involving the singlet DDW and the DSC pairings. The absence of nesting in the normal state dispersion leads to the particle-hole asymmetry in the single-particle excitation spectrum of the pure DDW state. This is reflected in the coexisting DDW and DSC states though the latter is characterized by the Bogoluibov quasi-particle bands- a characteristic feature of SC state. We solve the coupled gap equations self-consistently together with the equation to determine the chemical potential. We also calculate the thermodynamic and transport properties in the PG phase.The electronic specific heat displays non-Fermi liquid feature. We show that the PG and DSC are representing two competing orders as the former brings about a depletion of the spectral weight available for pairing in the anti-nodal region of momentum space. We also show the depletion of the spectral weight below Tc at energies larger than the gap amplitude. This is an important hallmark of the strong coupling superconductivity. Furthermore, the passage from normal state to the PG state at a fixed hole under-doping is shown to correspond to a non-sharp thermal phase transition.