Anisotropic Eliashberg theory of MgB2: Tc, isotope effects, superconducting energy gaps, quasiparticles, and specific heat

Hyoung Joon Choi, Marvin L. Cohen, Steven G. Louie

Research output: Contribution to journalArticle

56 Citations (Scopus)

Abstract

The anisotropic Eliashberg formalism, employing results from the ab initio pseudopotential density functional calculations, is applied to study the superconducting properties of MgB2. It is shown that the relatively high transition temperature of MgB2 originates from strong electron-phonon coupling of the hole states in the boron σ-bonds although the coupling strength averaged over the Fermi surface is moderate, and the reduction of the isotope effect arises from the large anharmonicity of the relevant phonons. The superconducting energy gap is nodeless but its value varies strongly on different pieces of the Fermi surface. The gap values Δ(k) cluster into two groups at low temperature, a small value of ∼2 meV and a large value of ∼7 meV, resulting in two thresholds in the quasiparticle density of states and an increase in the specific heat at low temperature due to quasiparticle excitations over the small gap. All of these results are in good agreement with corresponding experiments and support the view that MgB2 is a phonon-mediated multiple-gap superconductor.

Original languageEnglish
Pages (from-to)66-74
Number of pages9
JournalPhysica C: Superconductivity and its applications
Volume385
Issue number1-2
DOIs
Publication statusPublished - 2003 Mar 1

Fingerprint

Fermi surface
Isotopes
isotope effect
Specific heat
Energy gap
specific heat
heat
Fermi surfaces
Boron
Phonons
Superconducting materials
Superconducting transition temperature
Density functional theory
Temperature
pseudopotentials
Electrons
boron
phonons
transition temperature
formalism

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering

Cite this

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Anisotropic Eliashberg theory of MgB2 : Tc, isotope effects, superconducting energy gaps, quasiparticles, and specific heat. / Choi, Hyoung Joon; Cohen, Marvin L.; Louie, Steven G.

In: Physica C: Superconductivity and its applications, Vol. 385, No. 1-2, 01.03.2003, p. 66-74.

Research output: Contribution to journalArticle

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