On the existence of Rapid Oscillations in various phases of quasi one-dimensional $\mathrm{(TMTSF)_2PF_6}$

We report on the studies of magnetoresistance in $\mathrm{(TMTSF)_2PF_6}$. We have found that Rapid Oscillations of the magnetoresistance are absent in the metallic state and are present in the spin-ordered states solely, including both the lowest- and higher-order FISDW states. The spin-ordered state, which had previously been believed to be insulating, is not totally gapped; at least, at a finite temperature, there remains a vestigial Fermi surface comprising 2D metallic “pockets”. Our data agree qualitatively with the theory that considers the coexistence of two spin-density waves with two respective nesting vectors.