Giant superconducting anisotropy in Bi2Sr2Ca1Cu2O8+ delta.

Abstract

Using torque magnetometry, the superconducting anisotropy of a single crystal of ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{Ca}}_{1}$${\mathrm{Cu}}_{2}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ has been measured in the temperature range 77.5lTl83 K (${T}_{c}$=85 K). The data provide direct experimental evidence for a giant anisotropy. A London analysis provides an excellent description of the results and establishes a temperature-independent value of 3\ifmmode\times\else\texttimes\fi{}${10}^{3}$ for the superconducting effective-mass anisotropy.