Author:
Gupta Chandan,Parab Pradnya,Bose Sangita
Abstract
AbstractSuperconductivity in 3D Nb–Cu nanocomposite granular films have been studied with varying thickness for two different compositions, Nb rich with 88 at% of Nb and Cu rich with 46 at% of Nb. For both compositions, the superconducting transition temperature (Tc) decreases with decreasing film thickness. For any thickness, doubling the Cu content in the films decreases the Tc by about 2 K. To explore if phase fluctuations play any role in superconductivity in these 3D films, the superfluid stiffness (JS) of the films was measured using low frequency two-coil mutual inductance (M) technique. Interestingly, the measurement of M in magnetic fields showed two peaks in the imaginary component of M for both Nb rich and Cu rich films. The two peaks were associated with the pair-breaking effect of the magnetic field on the intra and inter-granular coupling in these films consisting of random network of superconductor (S) and normal metal (N) nano-particles. Furthermore, JS was seen to decrease with decreasing film thickness and increasing Cu content. However, for all films studied JS remained higher than the superconducting energy gap (∆) indicating that phase fluctuations do not play any role in superconductivity in the film thickness and composition range investigated. Our results indicate that an interplay of quantum size effects (QSE) and superconducting proximity effect (SPE) controls the Tc with composition in these 3D nano-composite films.
Funder
Science and Engineering Research Board
Publisher
Springer Science and Business Media LLC
Reference39 articles.
1. Tinkham, M. Introduction to Superconductivity (Dover Publications, Garden City, 2004).
2. Emery, V. J. & Kivelson, S. A. Importance of phase fluctuations in superconductors with small superfluid density. Nature 374, 434–437 (1995).
3. Kouh, T. & Valles, J. Deviations from mean-field behavior in disordered nanoscale superconductor-normal-metal-superconductor arrays. Phys. Rev. B 67, 140506 (2002).
4. Goldman, A. M. 40 Years of Berezinskii Kosterlitz Thouless Theory 135–160 (World Scientific, London, 2012).
5. Stewart, M. D., Yin, A., Xu, J. M. & Valles, J. M. Superconducting pair correlations in an amorphous insulating nanohoneycomb film. Science 318, 1273–1275 (2007).
Cited by
5 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献