Electron-phonon coupling and nontrivial band topology in noncentrosymmetric superconductors LaNiSi, LaPtSi, and LaPtGe

Abstract

The electronic structure and phonon properties of LaNiSi, LaPtSi, and LaPtGe have been studied using the first-principles density functional calculations. The electronic density of states near Fermi level of these compounds are dominated by the transition metal $d$ orbitals and Si/Ge $p$ orbitals, forming six sheets of Fermi surfaces. The asymmetric spin-orbit coupling lifts the spin degeneracies and creates four topological Weyl nodal rings around $X$ points, protected by the nonsymmorphic symmetry and time-reversal symmetry. The bare-electron susceptibility does not show a prominent feature, and electron-phonon coupling is sufficient to explain the observed superconductivity.