ANOMALOUSLY ENHANCED NOISE SPECTRAL DENSITIES OF YBCO MICRO-BRIDGE NEAR THE RESISTIVE TRANSITION REGION

Abstract

We have systematically measured the normalized noise power spectral density (Sn(f) = S(v)(f)/V2) of the YBCO microbridge and found V2/f(alpha) dependence. Near the zero resistance temperature (T(c,zero)), S(n)(f) increases more than eight orders of magnitude. Moreover, alpha changes from 1 to 2. Furthermore, once a magnetic field is applied, S(n)(f) showed a marked increase near T(c,zero). This anomaly is attributed to magnetic vortices coupled with the enhanced instability of space-time coherence associated with Cooper pair as a result of applied magnetic field, in addition to the thermal fluctuation.