Evidence from77SeKnight shifts for triplet superconductivity in(TMTSF)2PF6

We present 7 7 Se nuclear magnetic resonance (NMR) Knight shift (K) studies in pressurized (TMTSF) 2 PF 6 with a magnetic field aligned along the b axis, perpendicular to the conducting chains but parallel to the conducting plane. On cooling deep into the superconducting state, no observable change in K from both spin echo and free induction decay signal was found. This strongly suggests triplet superconductivity in (TMTSF) 2 PF 6 .