Delocalized quasiparticles in the vortex state of an overdoped high-T-c superconductor probed by Cu-63 NMR

作者：Zheng GQ^*; Ozaki H; Kitaoka Y; Kuhns P; Reyes AP; Moulton WG

来源：Physical Review Letters, 2002, 88(7): 077003.

DOI：10.1103/PhysRevLett.88.077003

We report the spin Knight shift (K-s) and the nuclear spin-lattice relaxation rate (1/T-1) in the vortex state as a function of magnetic field (H) up to 28 T in the high-T-c superconductor TlSr2CaCu2O6.8 (T-c = 68 K). At low temperatures well below T-c, both K-s and 1/T-1 measured around the middle point between the two nearest vortices (saddle point) increase substantially with increasing field, which indicate that the quasiparticle states with an ungapped spectrum are extended outside the vortex cores in a d-wave superconductor. The density of states (DOS) around the saddle point is found to be similar tokappaN(o)rootH/H-c2, with kappa = 0.5-0.7 and N-o being the normal-state DOS.

• 出版日期2002-2-18