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arXiv · 2410.09581

Optical Orientation of Mn$^{2+}$ Spins in Bulk (Zn, Mn)Se Induced by Magnetic Field

N. V. Kozyrev·K. A. Baryshnikov·B. R. Namozov·I. I. Kozlov·M. E. Boiko·N. S. Averkiev·Yu. G. Kusrayev
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Abstract

The optical orientation of Mn$^{2+}$ spins in the first excited state $^4$T$_1$ was experimentally observed in bulk (Zn, Mn)Se ($x_\mathrm{Mn}=0.01$) in the an external magnetic field of up to $6\,$T in Faraday geometry. This occurred during quasi-resonant continuous wave circularly polarized photoexcitation of the intracenter d-d transitions. A non-monotonic dependence of the thermal circular polarization of the intracenter photoluminescence on the magnetic field was observed. A theoretical model is proposed to describe the selection rules for resonant optical d-d transitions of an isolated Mn$^{2+}$ ion in a ZnSe cubic crystal. These rules are based on the analysis of the total angular momentum symmetry for the ground ($^6$A$_1$) and first excited ($^4$T$_1$) states of the Mn$^{2+}$ ion. This discussion neglects the specific mechanism for spin-flip processes in a d-shell of the ion during optical excitation. The analysis is founded on the rotational symmetry of the effective total angular momenta and parity for each state as a whole. Additionally, the Jahn-Teller coupling of the excited state orbital parts with tetragonal ($e$-type) local distortions of the crystal lattice is considered. This coupling results in the segregation of cubic axes and spin projections on these axes due to weak spin-orbit and spin-spin coupling in the excited state. This leads to energy splitting for spin states with their projections of $\pm 1/2$ and $\pm 3/2$ on each axis distinguished by specific Jahn-Teller distortion in the corresponding atomic potential minimum. By introducing two different times of relaxation to reach thermodynamic equilibrium for $\pm 1/2$ and $\pm 3/2$ states in each Jahn-Teller configuration, an angle dependent optical orientation contribution in photoluminescence polarization arises in the presence of a magnetic field.

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N. V. Kozyrev, K. A. Baryshnikov, B. R. Namozov, I. I. Kozlov, M. E. Boiko, N. S. Averkiev, Yu. G. Kusrayev. 2024-10-12. Optical Orientation of Mn$^{2+}$ Spins in Bulk (Zn, Mn)Se Induced by Magnetic Field. https://arxiv.org/abs/2410.09581

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