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Optical Conductivity (optical + conductivity)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Changes in optical properties of MnAs thin films on GaAs(001) induced by ,- to ,-phase transition

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008
B. Gallas
Abstract MnAs layers with 45 nm thickness were grown epitaxially on GaAs(001) substrates. Ellipsometry measurements were made in the spectral range 0.045 eV to 6 eV as a function of temperature (between ,10 °C and 50 °C) at 70° of incidence. In this way the transition from the hexagonal ,-phase to the orthorhombic ,-phase could be monitored. Non-zero off-diagonal elements of the Jones matrix for an azimuth of 38° off the [10] axis of the substrate indicate that the optical functions of MnAs are anisotropic in both phases. The optical conductivity exhibits low-energy interband transitions around 0.3 eV, more clearly seen in the ,-phase than in the ,-phase. Extrapolation of the optical conductivity to zero frequency confirms that the ,-phase is about two times more conducting than the ,-phase. A broad structure is observed in the visible range around 3 eV. The ,-phase is characterised by an anisotropy induced energy difference of this structure with a maximum at 2.8 eV for the extraordinary index and at 3.15 eV for the ordinary index. This difference vanishes in the ,-phase in which anisotropy mainly induces changes in amplitude of the 3 eV structure. The assignment of the structures will be discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Band structure and optical properties of SbSeI: density-functional calculation

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2007
Harun Akkus
Abstract The electronic structure and linear optical properties of the ferroelectric semiconductor SbSeI are calculated in the nonpolar phase using the density functional methods in the generalized gradient approximation. The obtained electronic band structure shows that SbSeI has an indirect forbidden gap of 1.65 eV. The linear photon-energy-dependent dielectric functions and some optical functions such as absorption and extinction coefficients, refractive index, energy-loss function, reflectivity and optical conductivity are calculated. Moreover, some important optical parameters such as the effective number of valence electrons and the effective optical dielectric constant are calculated. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Orbital polarons and optical conductivity in doped manganites

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2005
J. Ba
Abstract Orbital polaron formation and the optical conductivity ,(,) is investigated in the ferromagnetic and paramagnetic phases of doped (x = 1/4) manganites. Using finite-temperature diagonalization techniques for a realistic spin,orbital model we find the three-site correlations specific for the orbital polarized state and the ,(,) which is characterized by a broad spectrum with pronounced optical gap due to polaron formation. At small frequencies (, < t) the conductivity is dominated by an incoherent spectrum with spectral weight decreasing with increasing temperature leading to an activated behavior in resistivity above Tc. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Optical properties of NiCrOx thin films

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008
Nora Dahmouchène
Abstract The optical properties of thin NiCrOx layers were investigated by spectroscopic ellipsometry (SE). The layers were coated on float glass by magnetron sputtering at different oxygen partial pressures (20% to 30% oxygen in the sputtering gas) and the influence of the degree of oxidation was considered in details. The optical constants of the films n and k, in the visible to near infrared spectral range (0.35 to 1.7 mm), appear to be extremely sensitive to their chemical composition. Complementary studies were carried out using Fourier transform infrared ellipsometry (FTIR-SE) to determine the optical conductivity of the films and compare it with four-points-probe measurements. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Drude behavior in the far-infrared conductivity of cuprate superconductors ,

ANNALEN DER PHYSIK, Issue 7-8 2006
H.L. Liu
Abstract When viewed at frequencies below about 8 THz (250 cm -1; 30 meV) the ab -plane optical conductivity of the cuprate superconductors (in their normal state) is well described by a Drude model. Examples include optimally-doped YBa2Cu3O7-, and Bi2Sr2CaCu2O8; even the underdoped phases have a Drude character to their optical conductivity. A residual Drude-like normal fluid is seen in the superconducting state in most cases; the scattering rate of this quasiparticle contribution collapses at Tc. [source]