All-optical Control of the Magnetization in EuS, a Versatile Magnetic Insulator*

Finding new mechanisms of all-optical control of the magnetic state of matter is highly sought for the development of new devices and for optic based quantum computing. Recently we demonstrated that a single incident photon can generate several thousand spin coherent electrons in antiferromagnetic EuSe, by forming a supergiant spin polaron [1]. Because of the gigantic magnetic moment of the spin polaron, a tiny magnetic field can induce coherence in the spin polaron ensemble.
We extend this mechanism of magnetization control with few photons into other materials. Experimentally we show that in the Heisenberg ferromagnetic semiconductor EuS, near the Curie temperature, light induces spin polarons that are even larger than those observed in EuSe. Our Monte Carlo simulation offer a description of the magnetization process. The characteristic times of the spin polaron formation and extinction were measured using time-resolved pump-probe Faraday rotation. We shall present and discuss these results.

[1] A. B. Henriques et al, Phys. Rev. Lett. 120, 217203 (2018).