Anisotropic, multiband, and strong-coupling superconductivity of the Pb0.64Bi0.36 alloy

Abstract

This paper presents theoretical and experimental studies on the superconductivity of Pb${}_{0.64}$Bi${}_{0.36}$ alloy, which is a prototype of strongly coupled superconductors and exhibits one of the strongest coupling under ambient pressure among the materials studied so far. The critical temperature, the specific heat in the superconducting state, and the magnetic critical fields are experimentally determined. Deviations from the single-gap s-wave BCS-like behavior are observed. The electronic structure, phonons and electron-phonon interactions are analyzed in relation to the metallic Pb, explaining why the Pb-Bi alloy exhibits such a large value of the electron-phonon coupling parameter $\lambda \simeq 2$. Superconductivity is studied using the isotropic Eliashberg formalism as well as the anisotropic density functional theory for superconductors. We find that while Pb is a two-gap superconductor with well-defined separate superconducting gaps, in the Pb-Bi alloy an overlapped three-gap-like structure is formed with a strong anisotropy. Furthermore, the chemical disorder, inherent to this alloy, leads to strong electron scattering, which is found to reduce the critical temperature.

24 pages, 22 figures + supplemental material. Accepted for publication in Physical Review B. v3 - corrected error in Fermi velocity units conversion

References in corpus (13)

• 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
• Experimental demonstration of a two-band superconducting state for lead using scanning tunneling spectroscopy
• Retardation effects and the Coulomb pseudopotential in the theory of superconductivity
• Anisotropic superconducting gaps in YNi${}_2$B${}_2$C: A first-principles investigation
• NbIr${}_2$B${}_2$ and TaIr${}_2$B${}_2$ -- new low symmetry noncentrosymmetric superconductors with strong spin orbit coupling
• Gap Anisotropy in Multiband Superconductors Based on Multiple Scattering Theory
• Strong-coupling superconductivity of SrIr2 and SrRh2: Phonon engineering of metallic Ir and Rh
• Superconductivity near the Mott-Ioffe-Regel limit in the high-entropy alloy superconductor (ScZrNb)${}_{1-x}$(RhPd)${}_x$ with a CsCl-type lattice
• Electronic structure, electron-phonon coupling and superconductivity in noncentrosymmetric ThCoC2 from ab initio calculations
• Isotropic single gap superconductivity of elemental Pb: the `smiling' approach
• Pressure effects on the electronic structure, phonons, and superconductivity of noncentrosymmetric ThCoC2

Cited by in corpus (1)

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