Abstract
Although the pairing symmetry of the high-Tc superconductors is widely accepted to be dx2 − y2, measurements in apparent contradiction with this picture have been reported in Bi2Sr2Ca1Cu2O8 + x and attributed to s-wave symmetry or complex mixtures of s-wave and d-wave. To clarify this issue, we have measured the transport properties of asymmetric 45° [100]/[110] Bi2Sr2Ca1Cu2O8 + x bicrystal Josephson junctions, a geometry sensitive to the pairing symmetry. All samples investigated show complicated but polarity-symmetric modulation of their critical currents with magnetic field, providing unambiguous, clear evidence for a predominant dx2 − y2 pairing symmetry at Bi2Sr2Ca1Cu2O8 + x interfaces.