TRICRYSTAL EXPERIMENTS FOR TESTING PAIRING SYMMETRY IN CUPRATE SUPERCONDUCTORS

Based on macroscopic quantum coherence effects arising from pair tunne ling and flux quantization, a series of tricrystal experiments have be en designed and carried out to probe the microscopic phase of the pair wavefunction in high-T-c cuprate superconductors. By using a high-res olution scanning SQUID microscope, and the half-integer flux quantum e ffect in various tricrystal geometrical configurations, we have proven that the order parameter in YBa2Cu3O7 has nodes and lobes consistent with d-wave but not with the g-wave pairing symmetry.