Superconducting energy gaps, low temperature specific heat, and quasiparticle spectra of MgB2

Abstract

We report first-principles calculations of the k- and T-dependent superconducting gap Delta(k,T) in MgB2 and its manifestation in various measured quantities. Because the Fermi surface has disconnected sheets with different electron-phonon coupling strengths, our calculations show that near T=0, the values of Delta(k) cluster into two groups: large values (about 6.5 to 7.5 meV) on the strongly coupled sheets and small values (about 1 to 3 meV) on the weakly coupled sheets. The calculated gap, quasiparticle density of states, and specific heat and their temperature dependences are in agreement with the recent measurements which conclude that MgB2 is a multiple gap superconductor. In fact, theory predicts four prominent values for the gap at low T.

13 pages, 4 figures

References in corpus (21)

• Superconductivity of metallic boron in MgB_2
• Beyond Eliashberg superconductivity in MgB2: anharmonicity, two-phonon scattering, and multiple gaps
• Boron Isotope Effect in Superconducting MgB${}_2$
• Superconductivity of MgB2: Covalent Bonds Driven Metallic
• Electron-phonon interaction in the normal and superconducting states of MgB2
• Evidence for two superconducting energy gaps in MgB2 by point-contact spectroscopy
• Specific Heat of Mg ^{11}B_2
• Phonon dispersion and electron-phonon coupling in MgB_2 and AlB_2
• Giant anharmonicity and non-linear electron-phonon coupling in MgB${}_2$; A combined first-principles calculations and neutron scattering study
• Two Gap State Density in MgB${}_2$: A True Bulk Property or A Proximity Effect?
• First-Principles Calculation of the Superconducting Transition in MgB2 within the Anisotropic Eliashberg Formalism
• Specific heat in the superconducting and normal state (2-300 K, 0-16 Teslas), and magnetic susceptibility of the 38-K superconductor MgB2: evidence for a multicomponent gap
• The reduced total isotope effect and its implications on the nature of superconductivity in MgB2
• Evidence for Two Superconducting Gaps in $Mg{B}_2$
• Direct evidence for a multiple superconducting gap in MgB2 from high-resolution photoemission spectroscopy
• Scanning Tunneling Spectroscopy in MgB2
• Tunneling spectroscopy in small grains of superconducting MgB2
• Order parameter of MgB_2: a fully gapped superconductor
• High-Resolution Photoemission Study of MgB2
• Energy Gap from Tunneling and Metallic Sharvin Contacts onto MgB2: Evidence for a Weakened Surface Layer
• Tunneling spectroscopy measurement of the superconductor gap parameter of MgB_2