Harold N. Spector

Interaction of Acoustic Waves and Conduction Electrons

Publisher Summary This chapter attempts to give a systematic presentation of the theory of the acoustic phonon-conduction electron interaction as it stands today. It places particular emphasis on the effect of dc magnetic and electric fields on the electron-phonon interaction. It is restricted mainly to conduction electrons in spherical energy bands, thus ignoring the effects of complicated Fermi surfaces on the interaction. These effects have been covered in some detail in review articles by other authors and in articles on the Fermi surface. However, some discussion is given on the extension of the calculations to more general energy bands. This chapter concentrates mainly on presenting a clear physical picture of the interaction, with more emphasis on the theoretical aspects than on the experimental aspects. However, sufficient reference is made to experiments to illustrate the applicability of the theory. Reference is also made to the powerful tool this interaction represents in exploring the band structure of solids.

Optical absorption in crossed electric and magnetic fields

Abstract In the presence of crossed electric and magnetic fields, the optical absorption edge is shifted toward longer wavelengths. The deviation from its value in zero electric field is proportional to the sum of the effective masses in the two bands and also to the square of the electron drift velocity in the crossed fields. From the behavior of the absorption edge with d.c. electric field, the effective masses of the electrons in the conduction and valence bands can be determined. The period of the quantum oscillations in the optical absorption is also shifted by the same amount as the absorption edge from its value in zero electric field. The transition probability between different Landau levels in the two bands is found to be an oscillatory function of electric field. In very strong electric fields, the absorption increases with electric field.

Optical absorption in crossed electric and magnetic fields. II

Abstract The theory of optical absorption in crossed electric and magnetic fields is extended to take account of forbidden transitions in direct band gap semiconductors and of phonon assisted transitions in indirect band gap semiconductors. For the transitions which are forbidden at k = 0, the absorption edges and absorption peaks are shifted toward longer wavelengths by the electric field. The absorption coefficient is found to be an oscillatory function of electric field. In very strong electric fields, the absorption increases with electric field. For phonon assisted absorption there are two field dependent terms, one which is linear in the field and the other which is quadratic in field.