Critical Fluctuations in the Microwave Complex Conductivity of BSCCO and YBCO Thin Films

Abstract

Critical fluctuations above $T_c$ are studied in the microwave complex conductivity of BSCCO-2212, BSCCO-2223, and YBCO thin films. The analysis of the experimental data yields the temperature dependences of the reduced coherence length $\xi (T)/{\xi }_0$. Two critical regimes are observed, having the static critical exponent $\nu =1$ close to $T_c$, and a crosover to $\nu =2/3$ at higher temperatures. In more anisotropic superconductors the reduced coherence lengths are larger, and the critical states extend to higher temperatures.

4 pages, 3 figures