Far infrared reflectance of a mixed phase Y-Ba-Cu-O superconductor

The response of polycrystalline Tl–Ba–Ca–Cu–O superconducting thin films on short laser pulses has been investigated for radiation between 10 mgrm and 500 mgrm wavelength. Fast signals with time constants less than 1 ns were observed for wavelengths longer than about 100 mgrm whereas for shorter wavelengths only a bolometric signal could be detected

Energy Dependence of the Nernst-Ettingshausen Effect Induced By Pulsed Laser Light in Bismuth Films

The behavior with the irradiation energy and with the magnetic field of the thermomagnetic response induced by laser pulses in 5.5-μm Bi films at room temperature is reported in this paper. The Nernst-Ettingshausen coefficient at an applied magnetic field of 1 T is estimated: QNE≃1.0×10-5 V/T K. A good agreement is found when these results are compared with those reported earlier in polycrystalline bulk samples obtained by a conventional method. This supports the reliability of the pulsed laser technique in the measurement of weak transport effects and indicates that the optically pumped carriers hardly influence the transport properties of bismuth

Preparation, characterization, and far-infrared study of ceramic high-Tc superconductors

We report on a study of single-phase (superconducting) YBa2Cu3O7 and (nonconducting) Y2BaCuO5 and mixed phases of these compounds in bulk and film samples and on an investigation of ceramic bulk material of the homologous series Tl2Ba2CanCun+1O2n+6. We describe preparation and structural characterization by x-ray diffraction analyses and further characterization by electric, magnetic, tunnel junction, and Raman scattering studies, and we present results of far-infrared reflectivity measurements. In a theoretical analysis we relate the phonon structure of reflectivity spectra to geometric structure of a metallic network, with holes filled with nonconducting material. The influence of superconductivity on reflectivity is also investigated

Laser Scanning Microscopy of HTS Films and Devices

The work describes the capabilities of Laser Scanning Microscopy (LSM) as a spatially resolved method of testing high_Tc materials and devices. The earlier results obtained by the authors are briefly reviewed. Some novel applications of the LSM are illustrated, including imaging the HTS responses in rf mode, probing the superconducting properties of HTS single crystals, development of twobeam laser scanning microscopy. The existence of the phase slip lines mechanism of resistivity in HTS materials is proven by LSM imaging.Comment: 17 pages, 21 figures, Submitted to Fizika Nizkikh Temperatur (Low Temperature Physics

Thermopile effect due to laser radiation heating in thin films of high-Tc materials

We report on the observation of a thermopile effect caused by laser radiation heating in thin films of high-Tc material. The thermopile effect is due to a transverse Seebeck effect. The transverse Seebeck effect is observable first because of the anisotropy of YBa2Cu3O7−δ, and secondly because it is possible to grow off-axis epitaxial films. The thermopile effect can be used for developing detectors for laser radiation

Thermoelectric Effect in Normal-State YBa2Cu3O7-δ Films

Signal pulses of several 100 volts and currents of several amperes have been obtained at lateral surface contacts on normal-state YBa2Cu3O7-δ films in response to pulsed laser irradiation. The signals are shown to be of thermoelectric origin. Thermoelectric fields transverse to the laser-induced temperature gradient are due to the anisotropy of the thermopower in YBa2Cu3O7-δ giving rise to non-zero off-diagonal elements Sij propto α of the Seebeck tensor for films prepared with a tilt angle α between the film c-axis and the film surface normal. Large-tilt-angle films (up to α = 20°) could be grown on specially cut substrates and may be useful as almost wavelength-independent room temperature radiation detectors