STUDIES IN SOLID STATE THEORY, I. ULTRASONIC GENERATION IN METALS. II. INVERSION ASYMMETRY AND SPIN RESONANCE IN SEMICONDUCTORS
Abstract
In Part I a study of the free electron theory of direct generation of ultrasound in metals in a magnetic field B(,0) is presented. The amplitudes of the shear modes generated are calculated for both specular and diffuse scattering of electrons from the surface of the metal, supposed normal to (')B(,0). It is shown that for an electromagnetic wave incident along a direction for which the transverse-acoustic waves exhibit anisotropy, the amplitude of the shear modes varies nonmonotonically with the intensity of B(,0) independently of the scattering mechanism of the electrons at the surface of the metal. This is in contrast to the case of propagation along high-symmetry directions for which the transverse acoustic waves are degenerate where the non-monotonic behavior of the acoustic amplitude with B(,0) occurs only if the surface scattering is diffuse. Comparison with available experimental data is given. In Part II a study of the electron spin resonance in semiconduc- tors lacking inversion symmetry is presented. The anomalous dependence of the spin resonance intensity in n-InSb (zinc-blende structure) in the parallel Voigt geometry on the directions of the applied static magnetic field (')B(,0) and the wave vector (')q of the incident radiation, is explained in macroscopic terms by taking into account a (')q dependent dielectric function. In the microscopic picture this behavior is explained as an interference between electric-dipole and the less intense (')q dependent magnetic-dipole interactions, the former being allowed by virtue of mixing of Landau and Zeeman levels by a spin orbit interaction lacking inversion symmetry. The matrix elements for spin flip transitions in the perpendicular Voigt and Faraday geometrics are also presented. Finally, the study of spin transitions of donor bound electrons in wurtzite semiconductors is presented. We have thus, demonstrated the importance of inversion symmetry in the study of intraband and impurity state transitions in semiconductors.
Degree
Ph.D.
Subject Area
Condensation
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