Cyclotron resonance and strong phonon coupling inn-type ZnS at high magnetic fields up to 220 T

We have observed cyclotron resonance in the infrared wavelength range between 10.6 and 16.9 μm with pulsed high magnetic fields up to 220 T. The band-edge mass of n-type ZnS is ${\mathit{m}}^{\mathrm{*}}$=0.20±0.01${\mathit{m}}_0$ and the Fröhlich electron-phonon coupling constant α is 0.63 from a comparison with the experimental results of cyclotron resonance and a theoretical calculation based on the Wigner-Brillouin second-order perturbation theory. We have also observed phonon-assisted cyclotron resonance at the low-field side of the cyclotron resonance.