μSR Study of Unconventional Pairing Symmetry in the Quasi-1D Na₂Cr₃As₃ Superconductor

We report the finding of a novel pairing state in a newly discovered superconductor Na (Formula presented.) Cr (Formula presented.) As (Formula presented.). This material has a non-centrosymmetric quasi-one-dimensional crystal structure and is superconducting at (Formula presented.) 8.0 K. We find that the magnetic penetration depth data suggests the presence of a nodal line (Formula presented.) -wave pairing state with zero magnetic moment using transverse-field muon-spin rotation (TF- (Formula presented.) SR) measurements. The nodal gap observed in Na (Formula presented.) Cr (Formula presented.) As (Formula presented.) compound is consistent with that observed in isostructural (K,Cs) (Formula presented.) Cr (Formula presented.) As (Formula presented.) compounds using TF- (Formula presented.) SR measurements. The observed pairing state is consistent with a three-band model spin-fluctuation calculation, which reveals the (Formula presented.) spin-triplet pairing state with the (Formula presented.) pairing symmetry. The long-sought search for chiral superconductivity with topological applications could be aided by such a novel triplet (Formula presented.) p-wave pairing state.