THEORY OF RESONANT COUPLING BETWEEN LANDAU LEVELS AND LO PHONONS IN POLAR SEMICONDUCTORS .I. CYCLOTRON RESONANCE AND TRANSVERSE MAGNETORESISTANCE OF INSB

The coupling between the N =1 Landau level and the N =0 Landau level +one LO phonon continuum is investigated by the Green's function method under the condition that the cyclotron frequency ωc is nearly equal to the LO phonon frequency ω0. The spectral weigh function is shown to have a peak above the threshold of the continuum for any value of ωc, in contrast to the behavior of the solution of the WB perturbation and the pole of Green's function. Cyclotron resonance line profile is calculated as a function of ωc for ω<ω0 and at liquid nitrogen temperatures. Calculated line width is finite at ω=ω0 and decreases with temperature. Transverse magnetoresistance by absorption of thermal LO phonons is calculated as a function of ωc taking fully into account collision broadening of the N =1 Landau level due to LO phonon emission. The result is free of divergence at ωc=ω0. A shift of the position of the maximum to the high ωc side is predicted. Though qualitative agreement with experiment is good in the both phenomena, absolute magnitude of the line width and the magnetoresistance is smaller than the experimental one by a factor about 1.5, which suggests a larger value of the coupling constant than the one estimated from Fröhlich's formula. © 1969, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.