Origin of enhanced superconducting transition temperature through structural transformation in CaSi2

Abstract

Using the first-principles lattice dynamics, we have studied physical origin of enhancement in the superconducting transition temperature Tc of CaSi2 with structural phase transition. Optimization results show that CaSi2 has the AlB2 structure as an optimized structure above 17GPa. The electron-phonon interaction is enhanced, when CaSi2 takes the AlB2 structure compared to phase III. Especially, an E2g Einstein mode and a softened optical B2g mode are important. © 2008 IOP Publishing Ltd.