13C NMR study of vortex dynamics in LuNi2B 2C

Abstract

13C pulsed nuclear magnetic resonance (NMR) measurements have been performed on LuNi2B2C single crystals to investigate the vortex structure and dynamical behavior. The spectrum in the superconducting state significantly broadens by local field inhomogeneity due to a vortex lattice and then evolves to double peaks at low temperature. Both peaks shift toward low magnetic field due to imperfect field penetration whereas linewidth increases because of larger field inhomogeneity. Both the linewidth, reflecting vortex fluctuation, and the transverse relaxation rate 1/T2, probing slow motion of vortices, indicates significant thermal fluctuation of vortices in this low Tc and isotropic superconductor.