Related papers: Spin Dynamics in Cuprates: Optical Conductivity of…
Signatures of strong coupling effects in cuprate high-$T_{c}$ superconductors have been authenticated through a variety of spectroscopic probes. However, the microscopic nature of relevant excitations has not been agreed upon. Here we…
We have investigated the spin fluctuations at energy transfers up to ~110 meV, well above the resonance energy (33 meV) in the YBa2Cu3O6.5 ortho-II superconductor using neutron time-of-flight and triple-axis techniques. The spectrum at high…
Inelastic neutron scattering is used to investigate the collective magnetic excitations of the high-temperature superconductor parent antiferromagnet La2CuO4. We find that while the lower energy excitations are well described by spin-wave…
In the search for the mechanism of high-temperature superconductivity, intense research has been focused on the evolution of the spin excitation spectrum upon doping from the antiferromagnetic insulating to the superconducting states of the…
We calculated the optical conductivity $\sigma(T,\Omega)$ of a gas of Bogoliubov quasiparticles (BQP) from their Green's function and the Kubo formula. We compare with corresponding normal state (N) and superconducting state (SC) results.…
A first-order phase transition is found in the multilayer cuprate superconductor, HgBa$_2$Ca$_4$Cu$_5$O$_y$ (Hg-1245), with a superconducting transition temperature of 108 K, under zero magnetic field. We observed a hysteretic specific heat…
The optical conductivity of the one-band Hubbard model is calculated using the 'Dynamical Cluster Approximation' implementation of dynamical mean field theory for parameters appropriate to high temperature copper-oxide superconductors. The…
We report a temperature-dependent increase below 300 K of diffuse superlattice peaks corresponding to q_0 =(~2/5,0,0) in an under-doped YBa_2Cu_3O_6+x superconductor (x~0.63). These peaks reveal strong c-axis correlations involving the…
Within a two-band, strong coupling model we analyze SIS-tunneling conductance, Raman scattering and optical conductivity measured on $MgB_2$ samples. We find that features observed in tunneling and Raman spectroscopy at intermediate…
One of the interesting aspects of the CuO superconductors is that superconductivity is happening so close to the antiferromagnetic state. The nuclear magnetic resonance and the recent neutron scattering experiments clearly indicate that…
We report measurements of the specific heat and the thermal conductivity of the model Heisenberg spin-1/2 chain cuprate Sr$_{2}$CuO$_{3}$ at low temperatures. In addition to a nearly isotropic phonon heat transport, we find a quasi…
We present a 17O nuclear magnetic resonance study in the stoichiometric superconductor YBa_2Cu_4O_8. A double irradiation method enables us to show that, below around 180 K, the spin-lattice relaxation rate of plane oxygen is not only…
We calculate the optical conductivity of the CuO double chains of PrBa$_2$Cu$_4$O$_8$ by the mean-field approximation for the coupled two-chain Hubbard model around quarter filling. We show that the $\sim$40 meV peak structure, spectral…
Spin fluctuation-induced superconductivity in quasi-two dimensional organic compounds, \kappa-BEDT-TTF salts, is investigated within a fluctuation exchange (FLEX) approximation using a half-filled Hubbard model with a right-angled isosceles…
Band calculations show that a stripe-like anti-ferromagnetic spin wave is enforced by a 'half-breathing' phonon distortion within the CuO plane of HgBa_2CuO_4. This spin-phonon coupling is increased further by shear distortion and by…
Optical spectroscopy on single crystals of the new iron arsenide superconductor Ba{0.55}K{0.45}Fe2As2 shows that the infrared spectrum consists of two major components: a strong metallic Drude band and a well separated mid infrared…
The microwave conductivity of an ultra-pure single crystal of YBa$_2$Cu$_3$O$_{6.50}$ has been measured deep in the superconducting state as a continuous function of frequency from $0.5\to20$ GHz. Conductivity spectra were first measured at…
High-temperature superconductivity is reported in a series of compositionally-complex cuprates with varying degrees of size and spin disorder. Three compositions of Y-site alloyed YBa$_2$Cu$_3$O$_{7-x}$, i.e., (5Y)BCO, were prepared using…
We have measured the thermal conductivity of the spin S=1 chain compound Y2BaNiO5. Analyzing the anisotropy of the thermal transport allows to identify a definite spin-mediated thermal conductivity \kappa_s along the chain direction. The…
Pulsed NQR at the frequencies of 28-33 MHz has been used to study copper NQR spectra in YBa{2}Cu{3}O{7}, TmBa{2}Cu{3}O{7} and Y{0.9}Pr{0.1}Ba{2}Cu{3}O{7} compounds at temperatures of 4.2-200K. Quantitative analysis of the spectra has shown…