Magnetic-field enhancement of interface-phonon effects on quasi-two-dimensional magnetopolarons

Abstract

The binding energy of a polaron confined in the quantum well of GaAs/${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Al}}_{\mathit{x}}$As double heterostructures is calculated as a function of the magnetic field applied in the direction of growth. We have also calculated the oscillator strength of electron-phonon interaction for transitions from various excited states to the ground state of the polaron. Every type of optical-phonon mode that can exist in such structures within the continuum model is considered separately. It is found that the magnetic field greatly enhances the interface-phonon part of the polaron effect. For quantum wells of widths 150 A\r{} or smaller, the interface modes dominate all polaronic phenomena we have encountered when B\ensuremath{\gtrsim}1 T. For quantum wells of widths up to 100 A\r{}, contributions from confined bulk phonon modes are almost negligible in magnetic fields B\ensuremath{\gtrsim}1 T.