Article

# Measurement of magnetic penetration depth and superconducting energy gap in very thin epitaxial NbN films

Applied Physics Letters (Impact Factor: 3.52). 01/2010; 96. DOI: 10.1063/1.3314308

Source: arXiv

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**ABSTRACT:**We investigate the effects of mesoscopic inhomogeneities on the metal-superconductor transition occurring in several two-dimensional electron systems. Specifically, as a model of systems with mesoscopic inhomogeneities, we consider a random-resistor network, which we solve both with an exact numerical approach and by the effective medium theory. We find that the width of the transition in these two-dimensional superconductors is mainly ruled by disorder rather than by fluctuations. We also find that "tail" features in resistivity curves of interfaces between LaAlO3 or LaTiO3 and SrTiO3 can arise from a bimodal distribution of mesoscopic local Tc's and/or substantial space correlations between the mesoscopic domains.Physical review. B, Condensed matter 04/2011; 84. · 3.66 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**The microwave power density absorbed in the normal state by continuously irradiated superconducting Nb and NbN nanostrips is extracted from their electrical transport properties. The procedure is based on the reduction of the retrapping current (i.e., the minimum applied current required to sustain a dissipative region inside a superconducting microbridge) that results from the microwave dissipation. The power effectively absorbed by the nanostrips varies linearly with the input power level and falls in the μWμm–3 range. At a given microwave frequency, the relation between the input power and the absorbed power does not depend on the coolant temperature. In addition, the upper limit of the detection range is given by the heat removal capabilities through the substrate. When the absorbed microwave power exceeds this temperature-dependent heat removal threshold, normal hotspot domains are stabilized down to zero bias current. The determination of the microwave power absorbed by superconducting samples in the normal state may be of practical interest in the field of incident power detection.Journal of Applied Physics 09/2011; 110(5):053919-053919-8. · 2.21 Impact Factor -
##### Article: Phase Diagram and Upper Critical Field of Homogeneously Disordered Epitaxial 3-Dimensional NbN Films

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**ABSTRACT:**We report the evolution of superconducting properties with disorder, in 3 dimensional homogeneously disordered epitaxial NbN thin films. The effective disorder in NbN is controlled from moderately clean limit down to Anderson metal-insulator transition by changing the deposition conditions. We propose a phase diagram for NbN in temperature-disorder plane. With increasing disorder we observe that as k F l→1 the superconducting transition temperature (T c) and normal state conductivity in the limit T0 (σ 0) go to zero. The phase diagram shows that in homogeneously disordered 3-D NbN films, the metal-insulator transition and the superconductor-insulator transition occur at a single quantum critical point, k F l~1.Journal of Superconductivity and Novel Magnetism 05/2010; 24(1). · 0.93 Impact Factor

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