Coexistence of superconductivity and spin-density wave in (TMTSF)2ClO4: Spatial structure of the two-phase state

We report comprehensive (magneto) transport studies of the two-phase state in (TMTSF)(2)ClO4, where superconducting (SC) phase coexists with spin-density wave insulator (SDW). By tuning the degree of ClO4 anion ordering in controlled manner we smoothly suppress the SDW state and study resulting evolution of the SC phase spatial texture. We find that as SDW is suppressed, SC regions initially appear inside the SDW insulator in a form of filaments extended in the interlayer direction and further merge into the two-dimensional sheets across the most conducting axis of the crystal. We demonstrate that almost all our results can be explained within the soliton phase model, though with several assumptions, they can also be related with the creation of nonuniform deformations. We believe that the anisotropy is intrinsic to SC/SDW coexistence in various quasi-one-dimensional superconductors.