Optical investigation of magnetic order in monolayer semiconductors

In low-doped regions, the interaction between electrons dominates the behavior of individual electrons, forming correlated phases. Here, we experimentally study the spin correlation in electron-doped WSe2. With circular dichroism measurement, we demonstrate that long-range magnetic order can be stabilized by a circularly polarized optical pump. All optical manipulation of magnetic order allows us to study the dynamics of the magnetic order with optical pump-probe experiments. Utilizing a spatial resolved pump-probe experiment, we study the build-up dynamics of the magnetic order at spots several micrometers away from the pump. We also demonstrate that the initial pump-induced spin polarization is amplified by more than an order of magnitude due to the magnetic interaction. The research establishes the optical pump-probe experiment as a versatile tool in the study of correlated phases in two-dimensional electron gases and opens new applications of monolayer semiconductors in nanophotonics and spintronics.