| Inhomogeneous fluctuating superconductivity in YBa$_2$Cu$_3$O$_y$ and La$_{2-x}$Sr$_x$CuO$_4$ above $T_c$ (2009) | |||||||||
Abstract | |||||||||
| Over the past decade, a diverse set of experiments on high-transition temperature ($T_c$) cuprate superconductors have produced evidence for the existence of superconducting correlations at temperatures well above the bulk $T_c$. Included in this group of experimental findings is the discovery of an unusual magnetic-field induced effect in YBa$_2$Cu$_3$O$_y$ and La$_{2-x}$Sr$_x$CuO$_4$ above $T_c$ by transverse-field muon spin rotation (TF-$\mu$SR). The TF-$\mu$SR measurements show that an externally applied field induces a static internal magnetic field distribution, which persists to remarkably high temperatures above $T_c$. What is more, the inhomogeneous field distribution above $T_c$ tracks both $T_c$ and the superfluid density below $T_c$ over an extensive hole-doping range. Given that other experiments signify the presence of fluctuating amplitude and/or phase fluctuations of the superconducting order parameter in this region of the phase diagram above $T_c$, the observed presence of spatially non-uniform {\it static} internal fields of this kind is at first glance somewhat surprising. Here the key observations of the TF-$\mu$SR experiments are reviewed, and it is explained how the inhomogeneous line broadening above $T_c$ signifies the occurrence of non-uniform fluctuating superconductivity.. Comment: 18 pages, 6 figures | |||||||||
Publication details | |||||||||
| |||||||||