DOI: https://doi.org/10.30970/jps.02.509
EFFECT OF NONADIABATIC STATES CLOSE TO BRILLUOIN ZONE FACE ON VIBRATIONAL SPECTRUM
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Journal of Physical Studies 2(4), 509–517 (1998)
DOI: https://doi.org/10.30970/jps.02.509 EFFECT OF NONADIABATIC STATES CLOSE TO BRILLUOIN ZONE FACE ON VIBRATIONAL SPECTRUM |
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E. V. Zarochentsev
Donetsk Physico–Technical Institute,
National Academy of Sciences of Ukraine,
72, R. Luxemburg Str., Donetsk, UA–340114, Ukraine
Nonadiabatic states of electron–ion system close to Bragg plane play an important role in forming vibrational spectrum singularities in a crystal. In ordered matter the presence of nonadiabatic states causes drastic transformation of the behavior of nondiametral singularities near electron topological transition. This effect is most pronounced when phonon momentum connects two reconstructed parts of electron spectrum near a Bragg plane. Some polarization operator singularities lead to nonanalytic behavior of a phonon group velocity as a function of momentum under the conditions. These conditions are obtained in the present paper.