Electron-phonon superconductivity in CaBi2 and the role of spin-orbit interaction

Abstract

CaBi${}_2$ is a recently discovered type-I superconductor with $T_c=2$~K and a layered crystal structure. In this work electronic structure, lattice dynamics and electron-phonon interaction are studied, with a special attention paid to the influence of the spin-orbit coupling (SOC) on above-mentioned quantities. We find, that in the scalar-relativistic case (without SOC), electronic structure and electron-phonon interaction show the quasi-two dimensional character. Strong Fermi surface nesting is present, which leads to appearance of the Kohn anomaly in the phonon spectrum and enhanced electron-phonon coupling for the phonons propagating in the Ca-Bi atomic layers. However, strong spin-orbit coupling in this material changes the topology of the Fermi surface, reduces the nesting and the electron-phonon coupling becomes weaker and more isotropic. The electron-phonon coupling parameter $\lambda$ is reduced by SOC almost twice, from 0.94 to 0.54, giving even stronger effect on the superconducting critical temperature $T_c$, which drops from 5.2~K (without SOC) to 1.3~K (with SOC). Relativistic values of $\lambda$ and $T_c$ remain in a good agreement with experimental findings, confirming the general need for including SOC in analysis of the electron-phonon interaction in materials containing heavy elements.

11 pages, 7 figures, plus Supplemental Material

References in corpus (8)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Advanced capabilities for materials modelling with Quantum ESPRESSO
• BoltzTraP. A code for calculating band-structure dependent quantities
• Transport Properties and Diamagnetism of Dirac Electrons in Bismuth
• Superconductivity in CaBi${}_2$
• Superconducting Properties of BaBi${}_3$
• Origins of low- and high-pressure discontinuities of $T_c$ in niobium
• Ab-initio investigation of phonon dispersion and anomalies in palladium

Cited by in corpus (8)

• Strong-coupling superconductivity of SrIr2 and SrRh2: Phonon engineering of metallic Ir and Rh
• MgPd${}_2$Sb -- the first Mg-based Heusler-type superconductor
• Electronic structure, electron-phonon coupling and superconductivity in noncentrosymmetric ThCoC2 from ab initio calculations
• Effect of spin-orbit coupling on the zero-point renormalization of the electronic band gap in cubic materials: First-principles calculations and generalized Fröhlich model
• Electron-phonon coupling, critical temperatures and gaps in $\mathrm{NbS}{\mathrm{e}}_2$/$\mathrm{Mo}{\mathrm{S}}_2$ Ising Superconductors
• Chiral phonons in binary compounds $A$Bi ($A$ = K, Rb, Cs) with P2${}_1$/c structure
• Strong electron-phonon coupling in 3D tungsten nitride and coexistence of intrinsic superconductivity and topological nodal line in its 2D limit
• Chiral phonon in the cubic system based on the Laves phase of $A$Bi${}_2$ ($A=$K, Rb, Cs)