Upper critical field divergence induced by mesoscopic phase separation in the organic superconductor (TMTSF)(2)ReO4

摘要

Due to the competition of two anion orders, (TMTSF)(2)ReO4 presents a phase coexistence between semiconducting and metallic (superconducting) regions (filaments or droplets) in a wide range of pressures. In this regime, the superconducting upper critical field for H parallel to both c* and b' axes presents a linear part at low fields followed by a divergence above a crossover field. This crossover corresponds to the 3D-2D decoupling transition expected in filamentary or granular superconductors. The sharpness of the transition also demonstrates that all filaments are of similar sizes and self-organize in a very ordered way. The distance between the filaments and their cross sections are estimated.