Optical and hidden transport properties of BaFe1.91Ni0.09As2film

Real-Time Ellipsometry at High and Low Temperatures

Among the many available real-time characterization methods, ellipsometry stands out with the combination of high sensitivity and high speed as well as nondestructive, spectroscopic, and complex modeling capabilities. The thicknesses of thin films such as the complex dielectric function can be determined simultaneously with precisions down to sub-nanometer and 10^-4, respectively. Consequently, the first applications of high- and low-temperature real-time ellipsometry have been related to the monitoring of layer growth and the determination of optical properties of metals, semiconductors, and superconductors, dating back to the late 1960s. Ellipsometry has been ever since a steady alternative of nonpolarimetric spectroscopies in applications where quantitative information (e.g., thickness, crystallinity, porosity, band gap, absorption) is to be determined in complex layered structures. In this article the main applications and fields of research are reviewed.

Eliashberg Theory of a Multiband Non-Phononic Spin Glass Superconductor

I solved the Eliashberg equations for a multiband non-phononic s± wave spin-glass superconductor, calculating the temperature dependence of the gaps and of superfluid density. Their behaviors were revealed to be unusual: showing non-monotonic temperature dependence and reentrant superconductivity. By considering particular input parameters values that could describe the iron pnictide EuFe2(As1−xPx)2, a rich and complex phase diagram arises, with two different ranges of temperature in which superconductivity appears.