Effect of the Vortices on the Nuclear Spin Relaxation Rate in the Unconventional Pairing States of the Organic Superconductor (TMTSF)2PF6

This Letter theoretically discusses quasiparticle states and nuclear spin relaxation rates T₁^-1 in the quasi-one-dimensional superconductor (TMTSF)₂PF₆ under a magnetic field applied parallel to the conduction chains. We study the effects of Josephson-type vortices on T₁^-1 by solving the Bogoliubov de Gennes equation for p-, d- or f-wave pairing interactions. In the presence of line nodes in pairing functions, T₁^-1 is proportional to T in sufficiently low temperatures because quasiparticles induced by vortices at the Fermi energy relax spins. We also try to identify the pairing symmetry of (TMTSF)₂PF₆.