We investigated the electronic structures of the bandwidth-controlled ruthenates, Y2Ru2O7, CaRuO3, SrRuO3, and Bi2Ru2O7, by optical conductivity analysis in a wide energy region of 5 meV ∼ 12 eV. We could assign optical transitions from the systematic changes of the spectra and by comparison with the O 1s x-ray absorption data. We estimated some physical parameters, such as the on-site Coulomb ...

Abstract. In this communication we suggest a formulation of the optical conductivity as a convolution of an energy resolved joint density of states and an energy-frequency labelled transition rate. Our final aim is to develop a scheme based on the augmented space recursion for random systems. In order to gain confidence in our formulation, we apply the formulation to three alkaline earth titana...

The optical properties of the iron-chalcogenide superconductor K0.8Fe2−ySe2 with a critical temperature Tc = 31 K have been measured over a wide frequency range in the ab planes above and below Tc. The conductivity is incoherent at room temperature but becomes coherent (Drude-like) at T Tc; however, R 320 k , well above the threshold for the superconductor-insulator transition atR = h/4e2 6.9 k...

We report a direct measurement of the low-frequency optical conductivity of large-area single-crystal herbertsmithite, a promising spin-liquid candidate material, by means of terahertz time-domain spectroscopy. In the spectral range below 1.4 THz, we observe a contribution to the real part of the in-plane conductivity σ(ab)(ω) from the spin degree of freedom. This spin-induced conductivity exhi...

We introduce an approximate method which can be used to simulate the optical conductivity data of correlated multiband systems for normal and superconducting cases by taking advantage of a reversed process in comparison to a usual optical data analysis, which has been used to extract the electron-boson spectral density function from measured optical spectra of single-band systems, like cuprates...

The optical conductivity of undoped and low-doped YBa Cu O is studied in detail in the mid-infrared range. Full 2 3 6 16 18 Ž . Ž . isotope substitution of O with O is used to a study the optical phonons in the far-infrared and b identify the rich structure emerging in the mid-infrared from multiphonon and bimagnon-plus-phonon absorption. Substitution of Zn in the CuO planes allows direct obser...

– We study theoretically the optical conductivity of d-wave superconductors like in high temperature cuprates in the presence of impurities. We limit ourselves at T = 0K and focus on the frequency dependence of both σ1(ω) and ωσ2(ω) for ω . 2∆. When the impurity scattering is in the unitary limit, we find a peak in σ1(ω) with ω/∆ ≃ 0.1 ∼ 0.5, which may account for the peak seen by Basov et al. ...

The momentum average approximation is used to derive a new kind of nonperturbational analytical expression for the optical conductivity (OC) of a Holstein polaron at zero temperature. This provides insight into the shape of the OC, by linking it to the structure of the polaron's phonon cloud. Our method works in any dimension, properly enforces selection rules, can be systematically improved, a...

The frequencyand temperature-dependent optical conductivity of the copper oxide materials in the underdoped and optimal doped regimes are studied within the t-J model. The conductivity spectrum shows the unusual behavior at low energies and anomalous midinfrared peak in the low temperatures. However, this midinfrared peak is severely depressed with increasing temperatures, and vanishes at highe...

The ab-plane optical properties of the high-temperature superconductor Bi2Sr2CaCu2O8 are anisotropic in both the normal and the superconducting state. Consistent with the orthorhombic structure, the principal axes lie along the a and b crystallographic axes, nearly 45° from the Cu-O bond direction. In the normal state, analysis of the temperature-dependent optical conductivity suggests a scatte...