Critical currents of strongly disordered ultra-thin superconducting films

• Published in: Physica. B, Condensed matter Vol. 329; pp. 1386 - 1388
• Main Authors: Soman, Swati S., Gupta, K.Das, Chandrasekhar, N.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2003
• Subjects: Disorder; Josephson-junction; Quench-condensed; Josephson-junction; 74.25.Sv; 74.78.−w; Quench-condensed; 73.50.−h; Disorder
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/S0921-4526(02)02262-7

Quench-condensed films of various metals are well known systems for studying the superconducting state in presence of strong disorder. Critical currents of superconducting films of Bi and Sn with sheet resistance <500 Ω were found to vary with temperature according to the relation I c( T)= I c(0)(1−( T/ T c) 4). The result was found to be independent of the substrate used. The observed dependence implies a variation of the superconducting gap Δ( T)∼(1−( T/ T c) 4) 1/2, near T c. This is different from the behaviour of a BCS type gap near T c but consistent with some existing measurements on fabricated 2-D Josephson junction arrays. The I– V characteristics of these films also show hysteresis, indicating the presence of underdamped intergrain Josephson coupling. The values of the intergrain resistances and capacitances are estimated from the ratios of the observed retrapping and critical currents.