Abstract
Scanning tunneling microscope (STM) spectroscopy on the b– c plane of single crystals of an organic superconductor κ-(BEDT-TTF) 2Cu(NCS) 2 has been performed in superconducting and normal states with varying temperature. The temperature dependence of the zero-bias conductance d I/d V| V=0 is well explained by the d-wave gap model considering the T 2 dependence of the broadening parameter of the one-electron level Γ( T), which is obtained from the fitting of the d I/d V– V curves to the d-wave gap model. The d I/d V– V curve shows a broad dip around the Fermi energy above T c =10.4 K. This pseudogap structure remains up to about 45 K. The magnitude of the pseudogap is much larger than that of the superconducting gap Δ p ∼3 meV.
Published Version
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