In connection with the anomalous temperature dependence of the nuclear relaxation rate 1T1 of Cu in YBa2Cu3O7-y, the nuclear relaxation in the system is theoretically investigated, and the anomalous temperature dependence is found to be explained on the basis of the Bardeen-Cooper-Schrieffer (BCS) pairing, if the strong correlation effect of electrons is properly taken into account. The spin fluctuations make the superconducting state gapless near Tc and erase the hump of 1T1 which is usually observed in BCS superconductors. The spin-fluctuation vertex is highly renormalized in the superconducting state and thus 1T1, enhanced by the spin fluctuations in the normal state, is drastically suppressed in the superconducting state. The above two effects combined give a sharp decrease of 1T1 below Tc, which has been observed in the superconducting state of YBa2Cu3O7-y.
ASJC Scopus subject areas
- Condensed Matter Physics