Role of spin-orbit coupling on the physical properties of APb3 (A = Na, Ca, Y, and Th) superconductors

Structural, electronic, elastic, mechanical phonon and electron-phonon interaction properties of APb3 (A = Na, Ca, Y, and Th) superconductors have been investigated by using the density functional theory and the spin-orbit coupling (SOC) effects. It is found that the inclusion of SOC leads to significant changes in the electronic band structure of all the investigated compounds while the changes in the phonon properties essentially depend on the type of A atoms. While the phonon dispersion curves of YPb3 and ThPb3 are only weakly influenced, the inclusion of SOC produces significant amount of softening in the phonon dispersion curves for NaPb3 and CaPb3. Similarly, while the inclusion of SOC only weakly affects the electron-phonon interaction in YPb3 and ThPb3, it increases the electron-phonon coupling parameters in NaPb3 and CaPb3 by 27% and 33%, respectively. From the calculated elastic constants and related mechanical properties, all the superconductors studied are found to be ductile, which is favorable for their technological applications.