Fig. 1: Orbital torque and orbital pumping in 2D Janus dichalcogenides.
From: Orbital torques and orbital pumping in two-dimensional rare-earth dichalcogenides
a In 2D magnetic dichalcogenides (magnetization out of the plane along z, indicated with a black arrow), application of an electric field Ex along x (red arrow) leads to generation of a current of orbital angular momentum QL along y, polarized along z (small red arrows and yellow circular arrows) via the mechanism of the orbital Hall effect (OHE). b At the same time, due to broken z-reflection symmetry in Janus geometry, the electric field will give rise to a current-induced orbital polarization Lx (green arrow, as well as small red arrows and yellow circular arrows), which mediates an orbital torque on the magnetization along y (depicted with fading arrows). c In a reciprocal process, perturbing the magnetization with a torque Ty along y (grey arrow) will result in a generation of an orbital current along x polarized along y and z (shown with small yellow and red arrows), which constitutes the effect of in-plane orbital pumping. d For rare-earth dichalcogenides, the effect of orbital pumping is equivalent to the effect of orbital-to-orbital-current conversion, where the orbital current arises in response to an increasing linearly in time orbital field BL(t) applied along x (pink arrow). While the OHE can be used to generate orbital currents in 2D materials, the effect of orbital pumping mediated by orbital torque can be used to achieve orbital current generation by magnetization dynamics in 2D geometry.
