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Evidence from $^{77}$Se Knight shifts for triplet superconductivity in (TMTSF)$_2$PF$_6$

I. J. Lee·D. S. Chow·W. G. Clark·J. Strouse·M. J. Naughton·P. M. Chaikin·S. E. Brown
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Abstract

The layered quasi-one-dimensional molecular superconductor (TMTSF)$_2$PF$_6$ is a very exotic material with a superconducting order parameter whose ground state symmetry has remained ill-defined. Here we present a pulsed NMR Knight shift (K) study of $^{77}$Se measured simultaneously with transport in pressurized (TMTSF)$_2$PF$_6$. The Knight shift is linearly dependent on the electron spin susceptibility $χ_s$, and is therefore a direct measure of the spin polarization in the superconducting state. For a singlet superconductor, the spin contribution to the Knight shift, K$_s$, falls rapidly on cooling through the transition. The present experiments indicate no observable change in K between the metallic and superconducting states, and thus strongly support the hypothesis of triplet p-wave superconductivity in (TMTSF)$_2$PF$_6$.

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I. J. Lee, D. S. Chow, W. G. Clark, J. Strouse, M. J. Naughton, P. M. Chaikin, S. E. Brown. 2000-01-23. Evidence from $^{77}$Se Knight shifts for triplet superconductivity in (TMTSF)$_2$PF$_6$. https://arxiv.org/abs/cond-mat/0001332

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