The magnetooptical properties of InSe near the band gap

We have studied the magnetooptical properties of InSe near the band gap by wavelength modulation spectroscopy at 10 K with the electric vectorE perpendicular to theC-axis of the crystal. For the first time, Landau levels have been observed from which we obtain the reduced effective mass perpendicular to $\overrightarrow{C}$, μ_⊥ = (0.090 ± 0.010)m₀. The n = 1, 2 and 3 exciton lines along with a diamagnetic shift of the n = 1 level have been resolved from which we evaluate the Rydberg constant R = 15.0 ± 0.5 meV, the diamagnetic shift σ₁ = 14 ± 2 meV/(kG)² and ε_⊥ε_∥ = 81 ± 8. Evidence of the presence of the γ and ε polytypes in the sample due to stacking faults is given.