NMR and NQR studies of copper oxide superconductors.

Sup (63,65) Cu NMR and NQR measurements reveal remarkably different electronic character at the Cu(1) chain and Cu(2) plane sites in YBa sub 2 Cu sub 3 O sub (7.0). In the normal state, spin- lattice relaxation rates at both sites are strongly enhanced relative to estimated d-band Korringa (T sub 1) rates, but have sharply different temperature dependences. Moreover, T sub 1 anistropy is greater than an enhanced Korringa model can account for. Below T sub c, the temperature dependences reveal significantly different spectra for quasiparticle excitation at the two sites with the strongest apparent energy gap occurring for the planar Cu (sub 2) sites.