Node-like excitations in superconducting PbMo6S8 probed by scanning tunneling spectroscopy

Abstract

We present the first scanning tunneling spectroscopy study on the Chevrel phase PbMo6S8, an extreme type II superconductor with a coherence length only slightly larger than in high-Tc cuprates. Tunneling spectra measured on atomically flat terraces are spatially homogeneous and show well-defined coherence peaks. The low-energy spectral weight, the zero bias conductance and the temperature dependence of the gap are incompatible with a conventional isotropic s-wave interpretation, revealing the presence of low-energy excitations in the superconducting state. We show that our data are consistent with the presence of nodes in the superconducting gap.

To appear in PRB; 5 pages, 4 figures

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• Superconducting Chevrel phase PbMo${}_6$S${}_8$ from first principles
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