Magnetic Excitons

R. Lövenich, W. Schäfer, Peter Kner +1 more

Takami Tohyama

Yongyou Zhang, Lijie Shi, Guojun Jin +1 more

We study the quantum-well magnetoexcitons by the variational method in the strong coupling regime of excitons with microcavity photons. In such strong coupling regime, we find that the coupling between the exciton internal state and center of mass motion can be neglected. Through the calculations, we find that the magnetic field can reduce the exciton exchange interaction to 30% as Lw=30 nm with Lw being the quantum well width. This is in contrast to the magnetic-field enhancement in the exciton Rabi splitting. In this work, we obtain that a magnetic field can enhance the exciton Rabi splitting up to 1.6 times in the case of Lw=30 nm. They both originate from the local enhancement in the exciton internal state due to the magnetic field. In addition, we analyze the behavior of the magnetic response of the exciton energy, Rabi splitting, and exchange interaction in manipulating the polariton parametric scattering, and widening the microcavity applications.

Kai-Xuan Zhang, Min Zhang, Minjae Kim +25 more

The recently discovered magnetic exciton in the van der Waals (vdW) antiferromagnet NiPS3 exemplifies these phenomena, exhibiting several distinctive characteristics. Despite extensive investigation, much of its physics remains unresolved, with key questions about why the NiPS3 magnetic exciton is so sharp and optically bright despite the nominally spin-forbidden transition, posing significant challenges to a proper understanding and practical manipulation of the exciton. An urgent question is to what extent it is due to chemical disorder, magnetic weakening, lattice modification, or intrinsic instability of the bright exciton itself: answers to which will put stringent constraints on possible theoretical models. Here we address these questions using hydrostatic pressure as a clean, continuous, reversible, and in-situ tuning parameter. We find that the sharp photoluminescence peak is drastically suppressed by as little as 0.4 GPa and completely quenched by 1.5 GPa, with demonstrating its reversibility. Crucially, this bright-to-dark conversion occurs without magnetic, crystallographic, or electronic reconstruction despite an increase in the Neel temperature, as established by Raman, X-ray absorption, nuclear magnetic resonance spectroscopy, and first-principles many-body calculations. Our results demonstrate that the optical brightness of the magnetic exciton is independent of chemical disorder, lattice expansion, and weakening of magnetic order, indicating that a higher-order correlated mechanism governs the bright exciton. We further propose experimentally constrained microscopic scenarios involving exciton pairing, crystal-field-controlled spin-orbit mixing, and symmetry breaking, providing a framework for future tests of entangled magnetic exciton in correlated quantum magnets.

Karl W. Böer, Udo W. Pohl

Karl W. Böer, Udo W. Pohl