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

TL;DR

This study investigates critical fluctuations in the microwave complex conductivity of BSCCO and YBCO thin films, revealing two critical regimes with different static critical exponents and how anisotropy affects the critical states.

Contribution

It provides experimental analysis of critical fluctuations above Tc in high-temperature superconductor thin films, identifying two distinct critical regimes and their dependence on anisotropy.

Findings

Two critical regimes with exponents ν=1 and ν=2/3

Critical states extend to higher temperatures in more anisotropic superconductors

Reduced coherence lengths are larger in more anisotropic materials

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.