Evolution of magnetic circular dichroism of pure ZnTe in magnetic field: Spectral similarity between undoped and Cr-doped ZnTe

Abstract

Magnetic circular dichroism (MCD) spectra of pure ZnTe in various external magnetic field have been studied with first-principles calculations. By applying magnetic field on undoped semiconductor, the effects of spin splitting in host's bands due to $s,p\text{\ensuremath{-}}d$ exchange interactions in diluted magnetic semiconductors (DMSs) have been largely simulated. At the same time, the complexity of band structure in DMS is avoided since no magnetic ion is doped, which facilitates the band-to-band analysis of MCD spectra. The obtained MCD spectra of undoped ZnTe within low magnetic field are found to be proportional to the field strength and comparable with the experimental measurements. Within high magnetic field, where the Zeeman splitting is comparable with spin-orbit coupling strength, the MCD spectra become as similar as those of Cr-doped ZnTe around the $L$ critical points. Thus, the MCD signal contributed by the spin-splitted bands of host semiconductor is identified and separated from those due to the introduction of $\mathrm{Cr}\phantom{\rule{0.2em}{0ex}}3d$ or $4s$ impurity bands. These results indicate that the experimentally observed MCD spectra can be well reproduced and understood by band structure calculations.