Polaron cyclotron resonance observed forn-type ZnSe in high magnetic fields up to 180 T

We have observed cyclotron resonance and impurity cyclotron resonance (1s-2${\mathit{p}}^{+}$ transition) in a wide far-infrared wavelength range between 9.27 and 70.5 μm under pulsed high magnetic fields up to 180 T. A very large resonant polaron effect reflecting a large electron-phonon coupling constant was observed in both resonances, as well as a large nonparabolicity. The experimental results of cyclotron resonance were found to be in good agreement with a theoretical calculation based on the Wigner-Brillouin second-order perturbation theory taking account of the nonparabolicity. The impurity cyclotron-resonance data can also be well explained by a variational calculation. The donor ionization energy was found to increase by a factor of 2.39 at 180 T due to the magnetic freeze-out effect.