Scanning Tunneling Spectroscopy on the novel superconductor CaC6

Abstract

We present scanning tunneling microscopy and spectroscopy of the newly discovered superconductor CaC${}_6$. The tunneling conductance spectra, measured between 3 K and 15 K, show a clear superconducting gap in the quasiparticle density of states. The gap function extracted from the spectra is in good agreement with the conventional BCS theory with $\Delta (0)$ = 1.6 $\pm$ 0.2 meV. The possibility of gap anisotropy and two-gap superconductivity is also discussed. In a magnetic field, direct imaging of the vortices allows to deduce a coherence length in the ab plane ${\xi }_{ab}\simeq$ 33 nm.

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• Superconductivity of bulk CaC6
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• Muon spin rotation study of the magnetic penetration depth in the intercalated graphite superconductor CaC6
• Scanning microscopies of superconductors at very low temperatures
• Anisotropic superconductivity in graphite intercalation compound YbC6
• Tunneling into thin superconducting films: interface-induced quasiparticle lifetime reduction
• Linear and nonlinear electrodynamic response of bulk CaC6 in the microwave regime
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