Toward Two-Dimensional van der Waals Magnon Transport Devices: WTe ₂ Electrodes for Efficient Magnon Spin Injection and Detection

One of the bottlenecks toward all two-dimensional material-based magnon transport devices is the absence of a two-dimensional material for the efficient injection and detection of magnon spins. Here, we demonstrate that WTe₂, a layered, nonmagnetic van der Waals material, functions as an efficient spin injector and detector for magnon spins. It enables injection and detection of spins polarized in-plane via the conventional spin Hall effect and magnon spins polarized out-of-plane through unconventional charge-to-spin interconversion mechanisms. Such dual functionality is not achievable with conventional electrodes such as platinum or permalloy in the absence of a magnetic field. Using CrPS₄, an insulating two-dimensional antiferromagnet, we employ a hybrid nonlocal device geometry where magnon spins are injected and detected via conventional platinum and WTe₂ contacts. We find that the effective charge-to-spin conversion efficiency of WTe₂ is about 0.45 and 1.7 times for the injection of in- and out-of-plane polarized spins, respectively, compared to the in-plane polarized spin injection efficiency of platinum electrodes.