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arXiv · 0708.0921

Evidence for gap anisotropy in CaC6 from directional point-contact spectroscopy

R. S. Gonnelli·D. Daghero·D. Delaude·M. Tortello·G. A. Ummarino·V. A. Stepanov·J. S. Kim·R. K. Kremer·A. Sanna·G. Profeta·S. Massidda
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Abstract

We present the first results of directional point-contact spectroscopy in high quality CaC6 samples both along the ab plane and in the c-axis direction. The superconducting order parameter Δ(0), obtained by fitting the Andreev-reflection (AR) conductance curves at temperatures down to 400 mK with the single-band 3D Blonder-Tinkham-Klapwijk model, presents two different distributions in the two directions of the main current injection, peaked at 1.35 and 1.71 meV, respectively. By ab-initio calculations of the AR conductance spectra, we show that the experimental results are in good agreement with the recent predictions of gap anisotropy in CaC6.

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R. S. Gonnelli, D. Daghero, D. Delaude, M. Tortello, G. A. Ummarino, V. A. Stepanov, J. S. Kim, R. K. Kremer, A. Sanna, G. Profeta, S. Massidda. 2008-05-08. Evidence for gap anisotropy in CaC6 from directional point-contact spectroscopy. https://doi.org/10.1103/physrevlett.100.207004

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