Energy levels of an anisotropic three-dimensional polaron in a magnetic field - art. no. 235203

In the context of the improved Wigner-Brillouin theory, the energy Levels a re found of a Frohlich polaron in a uniaxial anisotropic polar semiconducto r with complex structure, placed in a magnetic field directed either along the optical axis or orthogonal to it. All sources of anisotropy that are co ntained in the shape of constant-energy surfaces of the bare electron, the electron-optical-phonon interaction, and the frequency spectrum of the extr aordinary phonon modes are considered. Analytical results for the electron- phonon interaction correction to the Landau levels below the optical-phonon continuum are given and, numerical results for the magnetic-field dependen ce of the cyclotron resonance frequency at low temperature are presented fo r the particular case of the layered semiconductors InSe and GaSe. Although the interaction between the bare electron and quasitransverse optical-phon on modes is weak, these modes play an important role in the pinning of Land au levels. The results given by Das Sarma for a two-dimensional isotropic m agnetopolaron are generalized to the anisotropic uniaxial case by taking fo rmally m(parallel to)-->infinity in the expression of the perturbed Landau levels found when the magnetic field is directed along the optical axis, m( parallel to) being the component of the bare-electron effective-mass tensor along the optical axis.