Precise determination of the in-plane superconducting anisotropy of (TMTSF)2ClO4

We report the in-plane anisotropy of the onset of superconductivity in the organic superconductor (TMTSF)2ClO4 in magnetic fields H accurately aligned to the most conductive ab′ plane. We revealed that the rapid increase of the onset fields at low temperatures occurs for both H∥a and H∥b′, in spite of the change in dimensionality of the electronic system due to the field-induced dimensional crossover. However, the overall behavior of the curves is qualitatively different, indicating that the superconducting states realized for H∥a and H∥b′ have different natures. Moreover, we observed that the rapid increase of the onset fields for H∥a is rather sensitive to the rotation of the magnetic field within the ab′ plane than that for H∥b′. This different dependence on the rotation of the magnetic field within the ab′ plane suggests that the suppression of the interlayer hopping plays an important role to realize the different superconducting natures for H∥a and H∥b′.

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