Magneto-optical studies of theZ1,2exciton-polaritons in CuI: Effects of finite exciton wave vector

Polarization-resolved magnetoreflectance spectra associated with the $Z_{1,2}$ (${\Gamma }_8\times {\Gamma }_6$) exciton states in CuI are measured up to 12 T. The appearance and the anisotropic Zeeman splitting of the reflectance anomaly originating from the (${\Gamma }_4, {\Gamma }_3$) exciton states are interpreted by means of the "$k$-linear term effect" on the $Z_{1,2}$ excitons in zinc-blende crystals. According to a recent theory which treats the reflectance line shape due to multicomponent polaritons, the measured results are quantitatively analyzed, providing the values of exciton parameters such as $\tilde{\kappa }$, ${\tilde{g}}_c$, ${\gamma }_2^{\mathrm{ex}}$, $\hslash K_l$, and exchange interactions. Magnetoluminescence spectra measured in the $Z_{1,2}$ excitons region and their unusual temperature change are well understood in this model which explains the contributions of the (${\Gamma }_4, {\Gamma }_3$) exciton polaritons to the normally observable ${\Gamma }_5$ lower and upper polariton luminescence bands.