INTERBAND MAGNETOOPTICAL STUDIES OF RESONANT POLARON COUPLING IN CDTECD1-XMNXTE QUANTUM-WELLS/

Magnetoreflectivity measurements of the 1s and 2s exciton energies in a CdTe/Cd1-xMnxTe superlattice have been made in magnetic fields up to 45 T, showing the resonant polaron coupling of electrons to LO phonon s. Strong reflectivity features are seen for both the 1s and 2s excito ns, which show a strong field-dependent spin splitting due to the dilu te magnetic barriers. At B-z=0, the 2s exciton feature is observed lyi ng 18 meV above the Is state, and is shifted upward in energy by the m agnetic fields. No resonant behavior occurs when the 2s state passes t hrough the LO-phonon energy of 21 meV, but at higher fields of around 20 T, the resonances for both spin states (sigma(+/-)) of the 2s excit on broaden and show a strong anticrossing behavior. These experiments are shown to be in excellent agreement with a theoretical treatment wh ich includes the resonant polaron coupling of the electrons alone. Bot h experiment and theory demonstrate an extremely strong resonant split ting of the 2s exciton states of approximately 11 meV, which is over 5 0% of the LO-phonon energy. The dominance of single-particle polaron c oupling is attributed to the relative sizes of the polaron (35 Angstro m A) and the exciton (50 Angstrom A) radius.