Is Semiconducting Transition-Metal Dichalcogenide Suitable for Spin Pumping?

Spin pumping has been reported on interfaces formed with ferromagnetic metals and layered transition-metal dichalcogenides (TMDs), as signified by enhanced Gilbert damping parameters extracted from magnetodynamics measurements. However, whether the observed damping enhancement purely arises from the pumping effect has remained debatable, given that possible extrinsic disturbances on the interfaces cannot be excluded in most of the experiments. Here, we explore an atomically clean interface formed with CoFeB and atomically thin MoSe2, achieved by an all in situ growth strategy based on molecular beam epitaxy. Taking advantage of ferromagnetic resonance analysis, we find that the Gilbert damping of the CoFeB/MoSe2 interface closely resembles that of CoFeB/SiO2, suggesting the absence of spin pumping. With similar findings demonstrated on a few more representative interfaces, this work clarifies the unsuitability of semiconducting TMDs for spin pumping and suggests that the observed damping enhancement in the previous reports may be predominantly attributed to extrinsic contributions during the experimental process.