On nonadiabatic effects in phonon spectra of metals
E.G. Maksimov a
A.E. Karakozov b
a Lebedev Physical Institute, Russian Academy of Sciences, Leninsky prosp. 53, Moscow, 119991, Russian Federation
b Institute for High Pressure Physics, Russian Academy of Sciences, Troitsk, Moscow, Russian Federation
Experimental and theoretical research on nonadiabatic effects in metals is briefly reviewed. It is shown that these effects are most manifest in optical phonon spectra at small
wave vectors q satisfying the condition qvF < ω0(q), where vF
is the electron Fermi velocity, and ω0(q) is the phonon frequency. Various theoretical approaches to calculating nonadiabatic effects are examined. Fröhlich’s phenomenological field-theoretical model, the most widely used in such calculations, is discussed in detail, some aspects of its application are considered, and its efficiency as a tool for studying nonadiabatic effects is demonstrated.