Charge Dynamics from Copper Oxide Materials

The charge dynamics of the copper oxide materials in the underdoped and optimal doped regimes is studied within the framework of the fermion-spin theory. The conductivity spectrum shows the non-Drude behavior at low energies and unusual midinfrared peak, and the resistivity exhibits a linear behavior in the temperature, which are consistent with experiments and numerical simulations.Comment: 10 pages, the figures are not included and can be air-mailed by reques

Doping and energy evolution of spin dynamics in the electron-doped cuprate superconductor Pr0.88_{0.88}LaCe0.12_{0.12}CuO4−δ_{4-\delta}

The doping and energy evolution of the magnetic excitations of the electron-doped cuprate superconductor Pr$_{0.88}$LaCe$_{0.12}$CuO$_{4-\delta}$ in the superconducting state is studied based on the kinetic energy driven superconducting mechanism. It is shown that there is a broad commensurate scattering peak at low energy, then the resonance energy is located among this low energy commensurate scattering range. This low energy commensurate scattering disperses outward into a continuous ring-like incommensurate scattering at high energy. The theory also predicts a dome shaped doping dependent resonance energy.Comment: 8 pages, 4 figures, added discussions, replotted figures, and updated references, accepted for publication in Phys. Rev.

Pseudogap effects on the c-axis charge dynamics in copper oxide materials

The c-axis charge dynamics of copper oxide materials in the underdoped and optimally doped regimes has been studied by considering the incoherent interlayer hopping. It is shown that the c-axis charge dynamics for the chain copper oxide materials is mainly governed by the scattering from the in-plane fluctuation, and the c-axis charge dynamics for the no-chain copper oxide materials is dominated by the scattering from the in-plane fluctuation incorporating with the interlayer disorder, which would be suppressed when the holon pseudogap opens at low temperatures and lower doping levels, leading to the crossovers to the semiconducting-like range in the c-axis resistivity and the temperature linear to the nonlinear range in the in-plane resistivity.Comment: 21 pages, Revtex, Six figures are include

Fermi surface topology and impurity-induced resonance state in BiS2_{2}-based superconductors

Within the two-orbital model for BiS$_{2}$-based superconductors, the effect from a single nonmagnetic impurity scattering on the superconducting-state is investigated in terms of the T-matrix approach. By considering three kinds of the typical Fermi surface topology which characterize the essential features of the doping dependence of the electronic structure in BiS$_{2}$-based superconductors, it is found that the impurity scattering on the superconducting-state with the conventional $s$-wave, the extended $s$-wave, the $\pm s$-wave, and the $d_{x^{2}-y^{2}}$-wave symmetries induces \textit{qualitatively} different resonance states due to the evolution of unique nodal structures on the Fermi surface with doping. These impurity-induced resonance states can be verified directly by the scanning tunneling microscopy experiments, and therefore they are proposed as a probe of the superconducting pairing symmetry in BiS$_{2}$-based superconductors.Comment: 5 pages, 7 figure

Influence of the additional second neighbor hopping on the spin response in the t-J model

The influence of the additional second neighbor hopping t' on the spin response of the t-J model in the underdoped and optimally doped regimes is studied within the fermion-spin theory. Although the additional second neighbor hopping t' is systematically accompanied with the reduction of the dynamical spin structure factor and susceptibility, the qualitative behavior of the dynamical spin structure factor and susceptibility of the t-t'-J model is the same as in the case of t-J model. The integrated dynamical spin structure factor spectrum is almost t' independent, and the integrated dynamical spin susceptibility still shows the particularly universal behavior as $I(\omega,T)\propto {\rm arctan}[a_{1}\omega/T+a_{3}(\omega/T)^{3}]$.Comment: 12 pages, Latex, Four figures are included, final published version [accepted for publication in Phys. Rev. B (July 1 issue)