Science Daily April 20, 2022
Recently two-dimensional moiré superlattices have emerged as a promising platform for quantum engineering. The power of the moiré system lies in the high tunability of its physical parameters by adjusting the layer twist angle, electrical field, moiré carrier filling and interlayer coupling. An international team of researchers (USA – University of Washington, Oak Ridge National Laboratory, Pacific Northwest National Laboratory, Hong Kong, Japan) found that optical excitation can highly tune the spin–spin interactions between moiré-trapped carriers, resulting in ferromagnetic order in WS2 /WSe2 moiré superlattices. Near the filling factor of −1/3, as the excitation power at the exciton resonance increases, a well-developed hysteresis loop emerges in the reflective magnetic circular dichroism signal as a function of magnetic field, a hallmark of ferromagnetism. The observed phenomenon points to a mechanism in which itinerant photoexcited excitons mediate exchange coupling between moiré-trapped holes. This discovery adds a dynamic tuning knob to the rich many-body Hamiltonian of moiré quantum matter…read more. TECHNICAL ARTICLE
Tuning the magnetic states using optical excitation power and filling factor. Credit: Nature volume 604, pages468–473 (2022)Â