Electron-phonon interaction in the normal and superconducting states of MgB2 - art. no. 020501

For the 40 K superconductor MgB2, we have calculated the electronic and pho nonic structures and the electron-phonon (e-ph) interaction throughout the Brillouin zone ab initio. In contrast to the isoelectronic graphite, MgB2 h as holes in the bonding sigma bands, which contribute 42% to the density of states: N(0) = 0.355 states/(MgB2)(eV) (spin). The total interaction stren gth, lambda = 0.87 and lambda (tr) = 0.60, is dominated by the coupling of the sigma holes to the bond-stretching optical phonons with wave numbers in a narrow range around 590 cm(-1). Like the holes, these phonons are quasi- two-dimensional and have wave vectors close to GammaA, where their symmetry is E. The pi electrons contribute merely 0.25 to lambda and to lambda (tr) . With Eliashberg theory we evaluate the normal-state resistivity, the dens ity of states in the superconductor, and the B-isotope effect on T-c and De lta (0), and find excellent agreement with experiments, when available. T-c = 40 K is reproduced with mu* = 0.10 and 2 Delta (0)/k(B)T(c) = 3.9. MgB2 thus seems to be an intermediate-coupling e-ph pairing s-wave superconducto r.