Abstract
The superconducting phase of organic superconductors κ-(BEDT-TTF)2Cu(NCS)2 and (MDT-TTF)2AuI2 was investigated by the electron tunneling spectroscopy using low temperature STM. The tunneling differential conductance at the lateral surface of κ-(BEDT-TTF)2Cu(NCS)2 varies its shape depending on the tip direction. The in-plane anisotropy of the conductance is well explained by the d-wave symmetry with line nodes along the direction 45° from the c-axis. For (MDT-TTF)2AuI2, the tunneling conductance at T = 1.4 K shows the superconducting energy gap structure clearly. The finite conductance inside the gap edge suggests the gap anisotropy. The tunneling spectrum is explained by the d-wave pairing. The obtained gap Δ0 = 2 meV (2Δ0/kT c = 12) is larger than that of the weak coupling limit. The pseudogap structure is observed near T c .
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Ichimura, K., Arai, T., Nomura, K. et al. STM Spectroscopy on Anisotropic Superconductors. Journal of Superconductivity 12, 519–523 (1999). https://doi.org/10.1023/A:1007732201440
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DOI: https://doi.org/10.1023/A:1007732201440