T4 to T2 resistivity transition and superconducting fluctuations in disordered VN films

Abstract

Thin films of Vn have been prepared with a wide range of structural disorder as characterized by residual resistivities from the clean value of ρ0=5.0 μΩ cm up to 100 μΩ cm. The disorder is primarily a consequence of nitrogen vacancies in as-made films or α-particle damage of clean, stoichiometric VN. We have observed a transition in the power-law dependence of the low-temperature resistivity from T4 to T2 as disorder increases, consistent with the universal behavior of strong-coupled superconductors proposed by Gurvitch. Comparison of this transition with the universal plot leads to an estimate of the electron-phonon coupling λp between 1.0 and 1.1. Disordered films also display an enhanced conductivity several degrees above Tc which is well described by a model of three-dimensional (3D) superconducting fluctuations. This represents one of the few cases where fluctuation enhanced conductivity has been observed in 3D films, other cases being the high-Tc oxides such as YBa2Cu3O7.

Source-reported materials — not catalogue approval

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