Eur. Phys. J. B 35, 13-20 (2003)
https://doi.org/10.1140/epjb/e2003-00251-y

A model Hamiltonian for MgB₂ which takes into account its unusual phononic features

¹ IMEM-CNR, Parco Area delle Scienze, 43100 Parma, Italy
² Unità INFM e Dipartimento di Fisica, Università di Parma, Parco Area delle Scienze, 43100 Parma, Italy

Corresponding author: ^a acquarone@fis.unipr.it

Received: 14 February 2003
Revised: 12 May 2003
Published online: 22 September 2003

Abstract

Taking as a starting point the results of LDA calculations, which show that in MgB₂ the phonons have a strong quartic anharmonicity and that the bond-stretching electron-phonon interaction (EPI) has both a linear and a large quadratic component, we propose a model Hamiltonian which successfully matches a number of experimental evidences. We relate the single critical temperature for both superconducting gaps to a phonon-induced inter-band coupling whose amplitude increases with temperature. We also obtain phonon frequencies and linewidths depending on the band filling, as well as band energies and hybridization amplitudes depending on the phonon number.