Migdal's theorem in heavy fermion systems

• Published in: Physica. B, Condensed matter Vol. 259; pp. 498 - 500
• Main Author: Wojciechowski, R.J
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1999
• Subjects: Electron–phonon interaction; Heavy fermion systems; Midgal's theorem; 71.27.+a; Electron–phonon interaction; 63.20K; Heavy fermion systems; Midgal's theorem
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/S0921-4526(98)00907-7

The problem of non-adiabaticity in strongly correlated electron systems has been a subject of considerable attention. We concentrate on the role of vertex corrections to electron–phonon interaction for heavy fermion systems in the normal state. The range of energy transfer important for heavy fermion systems is not set by the energy characteristic of phonons (Debye energy), as in the case of normal metals, but is determined by the characteristic energy scale T ∗ (spin fluctuation temperature). To preserve characteristic features of heavy fermion systems we introduce a very simple model assuming a huge density of states near the Fermi level and a very large electron effective mass. We present an estimate of the lowest-order vertex correction to electron–phonon interaction and show that the Migdal's theorem is not valid for heavy fermion systems.