Superconductivity in Heavy Alkaline-Earths Intercalated Graphites

Abstract

We report the discovery of superconductivity below 1.65(6) K in Sr-intercalated graphite SrC6, by susceptibility and specific heat (Cp) measurements. In comparison with CaC6, we found that the anisotropy of the upper critical fields for SrC6 is much reduced. The Cp anomaly at Tc is smaller than the BCS prediction indicating an anisotropic superconducting gap for SrC6 similar to CaC6. The significantly lower Tc of SrC6 as compared to CaC6 can be understood in terms of "negative" pressure effects, which decreases the electron-phonon coupling for both in-plane intercalant and the out-of-plane C phonon modes. We observed no superconductivity for BaC6 down to 0.3 K.

4 pages, 4 figures, submitted to Phys. Rev. Lett

References in corpus (4)

• Prediction of new crystal structure phases in metal borides: a lithium monoboride analog to MgB2
• Scanning Tunneling Spectroscopy on the novel superconductor CaC6
• Specific Heat of the Ca-Intercalated Graphite Superconductor CaC${}_6$
• Possibility of superconductivity in graphite intercalated with alkaline earths investigated with density functional theory

Cited by in corpus (3)

• Evidence for gap anisotropy in CaC6 from directional point-contact spectroscopy
• Far-infrared signature of the superconducting gap in intercalated graphite CaC6
• Pressure effects on the superconducting transition in nH-CaAlSi