Spatial characterization of the edge barrier in wide superconducting thin films
A.G. Sivakov, O.G. Turutanov, A,E. Kolinko, and A.S. Pokhila
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Nauky Ave., Kharkiv 61103, Ukraine
Received November 10, 2017
The paper discusses the issue of current-induced destruction of superconductivity in wide (whose width is much larger than the magnetic penetration depth) superconductive thin films in weak magnetic fields. We focus especially on the role of the edge potential barrier (Bean–Livingston barrier) and determination of the edge which is responsible for the critical state, at various mutual orientations of external normal magnetic field and transport current. Critical and resistive states of the thin film edge are visualized with the spatially-resolved technique of low-temperature laser scanning microscopy (LTLSM) that reveals the nearedge regions determining the critical current. A simple method based on these observations is elaborated to explore critical state at each edge of the thin film separately, and to estimate residual magnetic field in the cryostat. The proposed method requires no complicated LTLSM technique but only recording voltage-current characteristics in weak magnetic field. The in-formation being obtained in such a way is important particularly to treat experiments with superconductive thin-film single-photon detectors of optical irradiation.
PACS: 74.25.Sv Critical currents;
Key words: Bean–Livingston barrier, edge barrier, wide superconducting thin films, critical current, low-temperature laser scanning microscopy.
Published online: January 25, 2018