Unidirectional Magnetoresistance Driven by Nonequilibrium Antiferromagnetic Magnons

Magnetoresistive effects are typically symmetric under magnetization reversal. However, nonlinear spin transport can give rise to unidirectional magnetoresistance in systems with strong spin-orbit interaction and broken inversion symmetry. Here, we report a large magnonic unidirectional spin Hall magnetoresistance (USMR) in a van der Waals antiferromagnet CrPS4 in contact with Pt, driven by the nonequilibrium magnon accumulation with a finite magnon chemical potential. In contrast to conventional magnonic USMR driven by magnetization fluctuations, this effect persists under strong magnetic fields and low temperatures. The magnitude of magnonic USMR in CrPS4/Pt exceeds that of YIG/Pt by more than 2 orders of magnitude and surpasses the electrical USMR in metallic Ta/Co bilayers by a factor of 2. Our results highlight magnon chemical potential gradients for nonlinear magnetoresistance in antiferromagnetic van der Waals heterostructures and open a route to magnon-based antiferromagnetic spintronic functionalities in two-terminal device geometries.