Superfluid Spin Transport in the Van der Waals Antiferromagnet CrCl$_3$
Over the past decade, the quest for spin superfluidity has moved to the forefront of spintronics, driven by the promise of phase-gradient-driven, ultra-low-loss spin transport. However, experimental investigations remain limited, primarily due to the lack of suitable material systems. Here, we report on the discovery and control of a superfluid spin transport in the easy-plane van der Waals antiferromagnetic (AFM) insulator CrCl$_3$ by a nonlocal device structure. Combining nonlocal magnon transport measurements with theoretical modelling, we demonstrate that spin superfluidity emerges in CrCl$_3$ under canted AFM spin configurations, where it gives rise to ultra-long range (around 90 $μ$m), weakly decaying spin transport. We also provide direct evidence that strong magnetic fields and elevated temperatures suppress the superfluid state, restoring the rapid exponential decay with distance of incoherent magnons. These findings underscore the potential of spin superfluidity in two-dimensional magnetic insulators and establish CrCl$_3$ as a promising platform for energy-efficient, long-distance spin transport in next-generation spintronic applications.