Volume 42, Number 6, June II 1998
|Page(s)||667 - 672|
|Section||Condensed matter: electronic structure, electrical, magnetic and optical properties|
|Published online||01 September 2002|
Isotope effect on m* in high- materials due to the breakdown of Migdal's theorem
Dipartimento di Fisica, Università di Roma I
“La Sapienza”, Piazzale A. Moro, 2, 00185 Roma, Italy
Istituto Nazionale Fisica della Materia, Sezione di Roma 1 - Roma, Italy
2 Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
3 ICTP, P.O. Box 586 - 34100 Trieste, Italy
Accepted: 23 April 1998
We show that the inclusion of effects beyond Migdal's limit in the electron-phonon interaction naturally leads to an isotope effect for the effective mass m* of the charge carriers even much before reaching the polaron limit. This is the situation already considered in our approach to nonadiabatic superconductivity (Phys. Rev. Lett., 75 (1995) 1158). Such a result provides a scenario different from the polaronic one for the interpretation of the recently observed isotope effect on m* in and (Zhao et al., Phys. Rev. B, 51 (1995) 16487 and Nature, 385 (1997) 236).
PACS: 71.38.+i – Polarons and electron-phonon interactions / 74.25.Kc – Phonons / 71.18.+y – Fermi surface: calculations and measurements; effective mass, g factor
© EDP Sciences, 1998
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