Disappearance of superconductivity in ultra thin amorphous Nb films

✍ Scribed by Atsushi Asamitsu; Manabu Iguchi; Atsushi Ichikawa; Nobuhiko Nishida

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 151 KB
• Volume: 194-196
• Category: Article
• ISSN: 0921-4526
• DOI: 10.1016/0921-4526(94)91324-2

✦ Synopsis

The disappeara.nce of superconductivity in ultra thin amorphous Nb films has been studied by the measurements of the electrical sheet resistance _Rn and I-V characteristics. The mean field transition temperature T¢0amd the Kosterlitz-Thouless transition temperature TKThaVe been determined for films with various thickne.sses d . We have found that T~0's decrease linearly with d -1 and become zero near Rta,,, h/4e 2 = 6.45kf2/rn, the quantum resistance of pairing electrons. However TKT'S go to zero for the films with RNlower than h/(2e)2although their Tc0's are finite. It indicates that near the superconductorinsulator transition in uniformly disordered films the quantum fluctuations of the phase are of significance as well as the reduction of the amplitude of the superconducting order parameter.

We previou:31y reported that our amorphous Nb films exhibit the superconductor-insulator (SI) transition near RD,~ h/4e 2 = 6.45kf//t:] [1]. It was