Browsing by Author "Habtetsion, Semerab"

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    Peculiarities of the Electron-Phonon Interaction during Change of Topology of the Fermi Surface in Metals
    (Addis Ababa University, 1983-06) Habtetsion, Semerab
    The necessary background material for the analysis of the electron phonon interaction with respect to·the absorption coefficient and change in incident phonon frequency is discussed in the first and second chapters of this thesis. At the end of the second chapter the Migdal-Kohn Bnomalies for a spherical Fermi surface is dis~ussed. Experimental varification and phisical sense of these anomalies is also presented here. An investigation of the change in the phonon spectrum due to the Migdal-Kohn anomalies for some important cases of change in topology of the Fermi surface in metals is done in chapter three. In general it is found that the anomalies in rand Aw depend on the changes of the Fermi surface topology caused at phase transition of order 21. Also it ia noted that the singularities in rand Aw ~re interdependent as can be predicted by the Kramer's and Kronig relations