Ab initio study on the high superconducting transition temperature in calcium under high pressure

作者：Ishikawa T^*; Nagara H; Kusakabe K; Suzuki N

来源：High Pressure Research, 2009, 29(2): 204-207.

DOI：10.1080/08957950902723933

• first-principles calculation
• superconductivity
• phonon
• calcium

For calcium in the phases IV and V, we estimated the superconducting transition temperature Tc by the use of the Allen-Dynes formula. Setting the effective screened Coulomb repulsion constant * at 0.1 in the formula, we obtained Tc=23.42K at 100GPa for Ca-IV and Tc=15.87K at 120GPa for Ca-V. In order to clarify the origin of such high values of Tc, first, we investigated the band character of electrons and found that the high Tc is not necessarily related to the so called s-d transfer. Then we analyzed the electron-phonon coupling at each phonon mode in Ca-V where the highest Tc in elements has been experimentally observed. As a result, we discovered that an optical mode at the point has the strongest electron-phonon coupling. Such phonon mode can exist only in the complex crystal structure of Ca-V, and the result shows that the high Tc seems to be closely linked with the complex crystal structures like Ca-IV and Ca-V.

• 出版日期2009