Effects of anisotropy and disorder on the superconducting properties of niobium
We report results for the superconducting transition temperature and anisotropic energy gap for pure niobium based on Eliashberg’s equations and electron and phonon band structures computed from density functional theory. The electronic band structure is used to construct the Fermi surface and calcu...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2023-10-01
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| Series: | Frontiers in Physics |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fphy.2023.1269872/full |
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| author | Mehdi Zarea Hikaru Ueki J. A. Sauls |
| author_facet | Mehdi Zarea Hikaru Ueki J. A. Sauls |
| author_sort | Mehdi Zarea |
| collection | DOAJ |
| description | We report results for the superconducting transition temperature and anisotropic energy gap for pure niobium based on Eliashberg’s equations and electron and phonon band structures computed from density functional theory. The electronic band structure is used to construct the Fermi surface and calculate the Fermi velocity at each point on the Fermi surface. The phonon bands are in excellent agreement with inelastic neutron scattering data. The corresponding phonon density of states and electron–phonon coupling define the electron–phonon spectral function, α2F(p, p′; ω), and the corresponding electron–phonon pairing interaction, which is the basis for computing the superconducting properties. The electron–phonon spectral function is in good agreement with existing tunneling spectroscopy data except for the spectral weight of the longitudinal phonon peak at ℏωLO = 23 meV. We obtain an electron–phonon coupling constant of λ = 1.057, renormalized Coulomb interaction μ⋆ = 0.218, and transition temperature Tc = 9.33 K. The corresponding strong-coupling gap at T = 0 is modestly enhanced, Δ0 = 1.55 meV, compared to the weak-coupling BCS value Δ0wc=1.78kBTc=1.43meV. The superconducting gap function exhibits substantial anisotropy on the Fermi surface. We analyze the distribution of gap anisotropy and compute the suppression of the superconducting transition temperature using a self-consistent T-matrix theory for quasiparticle-impurity scattering to describe niobium doped with non-magnetic impurities. We compare these results with experimental results on niobium SRF cavities doped with nitrogen impurities. |
| first_indexed | 2024-03-11T14:50:24Z |
| format | Article |
| id | doaj.art-06fdc7d5803441bebacd0ac5fdea308f |
| institution | Directory Open Access Journal |
| issn | 2296-424X |
| language | English |
| last_indexed | 2024-03-11T14:50:24Z |
| publishDate | 2023-10-01 |
| publisher | Frontiers Media S.A. |
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| series | Frontiers in Physics |
| spelling | doaj.art-06fdc7d5803441bebacd0ac5fdea308f2023-10-30T09:30:38ZengFrontiers Media S.A.Frontiers in Physics2296-424X2023-10-011110.3389/fphy.2023.12698721269872Effects of anisotropy and disorder on the superconducting properties of niobiumMehdi ZareaHikaru UekiJ. A. SaulsWe report results for the superconducting transition temperature and anisotropic energy gap for pure niobium based on Eliashberg’s equations and electron and phonon band structures computed from density functional theory. The electronic band structure is used to construct the Fermi surface and calculate the Fermi velocity at each point on the Fermi surface. The phonon bands are in excellent agreement with inelastic neutron scattering data. The corresponding phonon density of states and electron–phonon coupling define the electron–phonon spectral function, α2F(p, p′; ω), and the corresponding electron–phonon pairing interaction, which is the basis for computing the superconducting properties. The electron–phonon spectral function is in good agreement with existing tunneling spectroscopy data except for the spectral weight of the longitudinal phonon peak at ℏωLO = 23 meV. We obtain an electron–phonon coupling constant of λ = 1.057, renormalized Coulomb interaction μ⋆ = 0.218, and transition temperature Tc = 9.33 K. The corresponding strong-coupling gap at T = 0 is modestly enhanced, Δ0 = 1.55 meV, compared to the weak-coupling BCS value Δ0wc=1.78kBTc=1.43meV. The superconducting gap function exhibits substantial anisotropy on the Fermi surface. We analyze the distribution of gap anisotropy and compute the suppression of the superconducting transition temperature using a self-consistent T-matrix theory for quasiparticle-impurity scattering to describe niobium doped with non-magnetic impurities. We compare these results with experimental results on niobium SRF cavities doped with nitrogen impurities.https://www.frontiersin.org/articles/10.3389/fphy.2023.1269872/fullelectronic structurephonon structurefirst-principles DFT calculationsEliashberg theoryelectron–phonon-mediated superconductivityanisotropic superconductors |
| spellingShingle | Mehdi Zarea Hikaru Ueki J. A. Sauls Effects of anisotropy and disorder on the superconducting properties of niobium Frontiers in Physics electronic structure phonon structure first-principles DFT calculations Eliashberg theory electron–phonon-mediated superconductivity anisotropic superconductors |
| title | Effects of anisotropy and disorder on the superconducting properties of niobium |
| title_full | Effects of anisotropy and disorder on the superconducting properties of niobium |
| title_fullStr | Effects of anisotropy and disorder on the superconducting properties of niobium |
| title_full_unstemmed | Effects of anisotropy and disorder on the superconducting properties of niobium |
| title_short | Effects of anisotropy and disorder on the superconducting properties of niobium |
| title_sort | effects of anisotropy and disorder on the superconducting properties of niobium |
| topic | electronic structure phonon structure first-principles DFT calculations Eliashberg theory electron–phonon-mediated superconductivity anisotropic superconductors |
| url | https://www.frontiersin.org/articles/10.3389/fphy.2023.1269872/full |
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