Orbital Magnetic Moment Dynamics and Hanle Magnetoresistance in Multilayered 2D Materials

The orbital Hall effect (OHE), resulting from non-trivial quantum geometry of 2D materials, has several potential advantages over the spin Hall effect (SHE), the latter being well known for its many applications in spintronics. Like the spin Hall effect, the OHE occurs in nonmagnetic materials without stringent symmetry requirements, but unlike the SHE it does no rely on relatively weak spin-orbit interaction. In 2D materials, these advantages risk to be nullified by the difficulty of turning the orbital moment away from the out-of-plane direction. Multilayered 2D materials offer a way out of this difficulty because the fluctuating in-plane component of the orbital moment, due to motion of electrons between the layers, can latch to a magnetic field. To describe this effect we have derived a semi-phenomenological equation of motion for the density of orbital magnetic moment in stacked 2D materials subjected to a magnetic field. Unlike the equations of motion for the spin, these equations produce a strongly anisotropic dynamics, which is governed by an inverse effective mass tensor for which we provide a fully microscopic expression. As a first application, we combine our equation of motion with phenomenological drift-diffusion equations to obtain a theory of orbital Hanle magnetoresistance in multilayered 2D materials.