NUCLEAR-SPIN RELAXATION VIA SPIN FLUCTUATIONS

We propose a hyperfine interaction between the copper nuclei and spinons to account for the nuclear spin relaxation (NSR) rates in the copper-oxygen plane. Based on the framework of the Zou-Anderson effective hamiltonian, we calculate the NSR rate 1/T1 of Cu spin in the superconducting compound YBa2Cu3O7-y using the gap equation of the spinon superfluid phase. The results show that 1/T1 decreases with temperature but there is no rapid increase over the normal relaxation rate just below the spinon superfluid transition temperature, in contrast with the conventional BCS prediction. The results suggest a possible explanation for the recent NSR experiments.