We report on infrared reflectivity measurements of the ab-plane response of superconducting Bi2Sr2CuO6 single crystals. The frequency dependent conductivity has a maximum near 500 cm at room temperature, which shifts to lower frequency and merges with a Drude peak below 100 K. We attribute the unusual behavior of the mid-infrared conductivity to low frequency transitions between electronic band...

A model dielectric function is derived for TiO2 based on reflection electron energy loss spectroscopy data and photoabsorption cross sections. The model is based on a set of Mermin oscillators. The input data is dominated by excitations at low momentum transfer, i.e. near the optical limit. Surprisingly the dielectric function derived at low momentum transfer describes the Compton profile quite...

The Casimir force is calculated between Au thin films that are described by a Drude model with a frequency dependent damping function. The model parameters are obtained from available experimental data for Au thin films. Two cases are considered; annealed and nonannealed films that have a different damping function. Compared with the calculations using a Drude model with a constant damping para...

Temperature dependent optical conductivities and dc resistivity of c-axis oriented superconducting (T(c) = 39.6 K) MgB2 films (approximately 450 nm) have been measured. The normal state ab-plane optical conductivities can be described by the Drude model with a temperature independent Drude plasma frequency of omega(p,D) = 13 600+/-100 cm(-1) or 1.68+/-0.01 eV. The normal state resistivity is fi...

The optical conductivity, σ(ω), of the two dimensional one-band Hubbard model is calculated at finite temperature using exact diagonalization techniques on finite clusters. The in-plane d.c. resistivity, ρab, is also evaluated. We find that at large U/t and temperature T, ρab is approximately linear with temperature, in reasonable agreement with experiments on high-Tc superconductors. Moreover,...

Monte Carlo–maximum entropy calculations of the conductivity of the infinite-dimensional periodic Anderson model are presented. We show that the optical conductivity displays anomalies associated with the exhaustion of conduction-band states near the Fermi energy including a Drude weight, which rises with temperature, with weight transferred from a temperature and doping-dependent mid-infrared ...

We report a comprehensive THz, infrared and optical study of Nb-doped SrTiO3 as well as dc conductivity and Hall effect measurements. Our THz spectra at 7 K show the presence of an unusually narrow (<2 meV) Drude peak. For all carrier concentrations the Drude spectral weight shows a factor of three mass enhancement relative to the effective mass in the local density approximation, whereas the s...

We consider a spin chain given by the XXZ model with a weak next-to-nearest-neighbor perturbation that breaks its exact integrability. We prove that such a system has an ideal metallic behavior (infinite conductivity), by rigorously establishing strict lower bounds on the zero-temperature Drude weight, which are strictly positive. The proof is based on exact renormalization group methods allowi...