Valence band parameters of cubic zinc selenide derived from magnetoreflectance of the Γ6 ? Γ8 exciton

Magnetoreflectance measurements on the Γ₆ ? Γ₈ free exciton ground state in cubic ZnSe in magnetic fields up to 18 Tesla are reported. The diamagnetic shift rate of the ground state components: $\text{|}\text{3}\text{2}\text{>β}$, $\text{|?}\text{3}\text{2}\text{>α}$, $\text{|}\text{1}\text{2}\text{>β}$ and $\text{|?}\text{1}\text{2}\text{>α}$ yield γ₂ = 0.53 ± 0.07 and an exciton reduced mass μ₀ = 0.117 ± 0.003, corresponding to γ₁ = 2.30 ± 0.45 for m_e¹ = 0.16 m₀. γ₁, γ₂ and an effective hole g-value $\text{κ}\text{tilde}\text{= -0.21}$ yield γ₃ = 0.82 ± 0.16 in the parabolic approximation and in agreement with the observed splitting of the $\text{|?}\text{3}\text{2}\text{>α}$, $\text{|?}\text{1}\text{2}\text{>β}$ states for B ∥ 110]. Taking into account polaron effects we derive bare valence band parameters γ₁^L = 2.71 ± 0.60, γ₂^L = 0.63 ± 0.09 and γ₃^L = 0.97 ± 0.21 from the renormalized parameters γ_i. The present results are considerably smaller than earlier theoretical calculations suggest, however they are in good agreement with a recent detailed analysis of two-photon absorption data for 2P exciton states.