Evidence for Bardeen-Cooper-Schrieffer-type superconducting behavior in the electride (CaO)12(Al2O3)7:e− from heat capacity measurements

Yoshimitsu Kohama; Sung Wng Kim; Takeo Tojo; Hitoshi Kawaji; Tooru Atake; Satoru Matsuishi; Hideo Hosono

doi:10.1103/PhysRevB.77.092505

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Evidence for Bardeen-Cooper-Schrieffer-type superconducting behavior in the electride (CaO)12(Al2O3)7:e− from heat capacity measurements

Yoshimitsu Kohama, Sung Wng Kim, Takeo Tojo, Hitoshi Kawaji, Tooru Atake, Satoru Matsuishi, Hideo Hosono

DOI 10.1103/PhysRevB.77.092505 · Physical Review B

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Abstract

The heat capacity of the single crystalline electride of (CaO)12(Al2O3)7:e− (C12A7:e−) with Tc=0.2K was larger than that of electron-undoped C12A7 in the temperature range 0.085–5K, reflecting the metallic nature of the electride. A superconducting transition was detected as a heat capacity jump ΔCp=3.4mJmol−1K−1, and the profile and magnitude of ΔCp agreed well with those expected from the BCS theory. The electron-phonon coupling constant (λ∼0.46) and Debye temperature (ΘD∼630K) were much larger than those for alkali metals having s-like conduction electrons as in the present electride, suggesting that electrides having a rigid structure will be a class of BCS superconductors.