三元硅化物CaAlSi的电-声子耦合和超导电性研究

应用全势线性缀加平面波方法计算新超导体CaAlSi的电子能带结构,用带心冻结声子法计算了声子频率及电声子耦合常数,并讨论了它们的超导电性.考虑到Al,Si原子分布的无序性和完全等价性,我们采用了双层超格子原胞模型,并考虑了低频B1g1声子频率的非谐性效应.由此计算得到稳定的低频B1g1声子频率为110cm-1,对超导电性有较大的贡献的Cad态电子与B1g1振动模式间的电声子耦合常数为0.37.我们的结果与用虚晶近似的结果是一致的.并证明CaAlSi的超导电性可由中等耦合的BCS理论来解释.

ELECTRON-PHONON COUPLING AND SUPERCONDUCTIVITY OF TERNARY SILICIDE CaAlSi

We use FP-LAPW method to study the electronic band structure of new superconductor CaAlSi. Phonon frequencies and electron-phonon coupling constant are calculated via zone-center frozen phonon calculations. Considering the randomly distributed of Al and Si atoms not only over the in-plane but also along the c direction,we chose the simplest double cell model for the stable ternary silicide. Considering the anharmonicity of phonon frequency, we obtain the phonon frequency of B1g1 mode to be 110cm^-1, and the electron-phonon coupling constant between Ca d electron and B1g1 phonon mode is 0.37, and A = 0. 73. The calculated results are consistent with that by using the model of virtual-crystal approximation, and proved that the superconductivity in CaAlSi can be well explained by the standard BCS theory in the moderate electron-phonon coupling strength.