Strong electron-phonon coupling in superconducting MgB2: A specific heat study - art. no. 172515

We report on measurements of the specific heat of the recently discovered s uperconductor MgB2 in the temperature range between 3 and 220 K. Based on a modified Debye-Einstein model, we have achieved a rather accurate account of the lattice contribution to the specific heat, which allows us to separa te the electronic contribution from the total measured specific heat. From our result for the electronic specific heat, we estimate the electron-phono n coupling constant lambda to be of the order of 2, significantly enhanced compared to common weak-coupling values less than or equal to0.4. Our data also indicate that the electronic specific heat in the superconducting stat e of MgB2 can be accounted for by a conventional, s-wave type BCS model.