Determination of excitonic parameters of theApolariton of CdS from magnetoreflectance spectroscopy

Abstract

The magnetoreflectance of the $A$ exciton of CdS is studied for fields up to 10 tesla for the orientations $\overrightarrow{\mathrm{H}}\perp \overrightarrow{\mathrm{c}}$ and $\measuredangle (\overrightarrow{\mathrm{H}}, \overrightarrow{\mathrm{c}})=45\mathrm{}°$. A quantitative line-shape analysis is made of the spectra using the model of polaritons with spatial dispersion and Pekar's $\mathrm{abc}$ and, considering damping and exciton-free surface layer it shows a remarkable good agreement between experiments and calculations. This allows a very distinct investigation of the splitting parameters of the exciton and the corresponding bands. The $g$ values are measured to be $g_{e\perp }=g_{e\parallel }=1.75\mathrm{}\pm 0.05$ and $g_{A\parallel }=1.25\mathrm{}\pm 0.1$. The longitudinal-transverse $\mathrm{H}\left({\Delta }_{\mathrm{LT}}\right)$ and, for the first time, the singlet-triplet splitting (${\Delta }_{56}$), both resulting from exchange interaction, are determined to ${\Delta }_{\mathrm{LT}}=(2.1\mathrm{}\pm 0.03)$ meV and ${\Delta }_{56}=(0.2\mathrm{}\pm 0.03)$ meV.