Experimental Evidence of a Dimensional Crossover in Y1Ba2Cu3O7−δ

Abstract

High-resolution torque-magnetometry data have been obtained on an untwinned single crystal of ${\mathrm{Y}}_1{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ in the temperature range $63<T<\mathrm{}88\mathrm{}$ K ($T_c=90.5\mathrm{}$ K). At $T=80\mathrm{}$ K and above, the data are fitted extremely well with the accepted three-dimensional phenomenological theory, but below this temperature an anomalous torque develops when the magnetic field lies close to the Cu-O planes. The qualitative and quantitative features of our results provide strong evidence that breakdown of the three-dimensional description below 80 K is associated with a crossover to two-dimensional superconducting behavior.