Tunneling spectroscopy on the organic superconductor κ-(BEDT-TTF)2Cu(NCS)2 using STM -: art. no. 104518

STM spectroscopy on the organic superconductor kappa-(BEDT-TTF)(2)Cu(NCS)(2) has been performed in the superconducting state with the use of single crystals. The anisotropy of the superconducting gap has been investigated both on the b-c plane, which is parallel to the two-dimensional conducting layers, and on the several surfaces perpendicular to the b-c plane. The tunneling spectra observed on the b-c plane are well explained by the anisotropic gap with the d-wave symmetry. The spectra on the lateral surfaces are also consistent with the d-wave gap with line nodes along the direction pi /4 from the k(b) and k(c) axes considering the k dependence of the tunneling transition probability. These results strongly indicate that the superconducting pair wave function in this salt has the d(x)2(-y)2-wave symmetry.