We present a study of the superconducting transition in MgB2 using the ab initio pseudopotential density- functional method, a fully anisotropic Eliashberg equation, and a conventional estimate for μ*. Our study shows that the anisotropic Eliashberg equation, constructed with ab initio calculated momentum-dependent electron-phonon interaction and anharmonic phonon frequencies, yields an average electron-phonon coupling constant λ=0.61, a transition temperature Tc=39 K, and a boron isotope-effect exponent αB=0.32. The calculated values for Tc, λ, and αB are in excellent agreement with transport, specific-heat, and isotope-effect measurements, respectively. The individual values of the electron-phonon coupling λ(k→,k→′) on the various pieces of the Fermi surface, however, vary from 0.1 to 2.5. The observed Tc is a result of both the raising effect of anisotropy in the electron-phonon couplings and the lowering effect of anharmonicity in the relevant phonon modes.
|Number of pages
|Physical Review B - Condensed Matter and Materials Physics
|Published - 2002 Jul 1
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics