Theoretical evidences for enhanced superconducting transition temperature of CaSi${}_2$ in a high-pressure AlB${}_2$ phase

Abstract

By means of first-principles calculations, we studied stable lattice structures and estimated superconducting transition temperature of CaSi${}_2$ at high pressure. Our simulation showed stability of the AlB${}_2$ structure in a pressure range above 17 GPa. In this structure, doubly degenerated optical phonon modes, in which the neighboring silicon atoms oscillate alternately in a silicon plane, show prominently strong interaction with the conduction electrons. In addition there exists a softened optical mode (out-of-plan motion of silicon atoms), whose strength of the electron-phonon interaction is nearly the same as the above mode. The density of states at the Fermi level in the AlB${}_2$ structure is higher than that in the trigonal structure. These findings and the estimation of the transition temperature strongly suggest that higher $T_{\mathrm{c}}$ is expected in the AlB${}_2$ structure than the trigonal structures which are known so far.

6 pages and 11 figures

References in corpus (5)

• Phonons and related properties of extended systems from density-functional perturbation theory
• Superconductivity of metallic boron in MgB_2
• Electron-phonon interactions and related physical properties of metals from linear-response theory
• Phonon dispersion and electron-phonon coupling in MgB_2 and AlB_2
• Electronic and structural properties of superconducting MgB${}_2$, CaSi${}_2$ and related compounds

Cited by in corpus (1)

• Pair-Hopping Mechanism for Layered Superconductors