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Session Q10 - HTSC: THEORY OF OBSERVATION OF ORDER PRAMETER SYMETRY
Mixed session, Friday morning, March 24, 8:00
Ballroom A4, San Jose Convention Center
Using a tunneling Hamiltonian approach we discuss the role of anisotropy in the tunneling matrix element in producing strongly varying DC Josephson currents as a function of the orientation of the crystal axes on both sides of the junction. We model a 2D system with an open normal Fermi surface which has nodes both for extended s -wave pairing ( \Delta_k=\Delta(\cos k_x+\cos k_y) ) and d_x^2-y^2 -wave pairing ( \Delta_k=\Delta(\cos k_x-\cos k_y) ) . Combined with the calculated conductivity peaks for quasiparticle tunneling in the superconducting state and the normal state conductivity we find for both pairing types a characteristic behaviour depending on the anisotropy of the tunneling Hamiltonian. We discuss our findings in relation with recent experiments on bicrystal grain boundary junction experiments on YBa _2 Cu _3 O _7 .