Dynamical criticality of spin-shear coupling in van der Waals antiferromagnets

The interplay between a multitude of electronic, spin, and lattice degrees of freedom underlies the complex phase diagrams of quantum materials. Layer stacking in van der Waals (vdW) heterostructures is responsible for exotic electronic and magnetic properties, which inspires stacking control of two-dimensional magnetism. Beyond the interplay between stacking order and interlayer magnetism, we discover a spin-shear coupling mechanism in which a subtle shear of the atomic layers can have a profound effect on the intralayer magnetic order in a family of vdW antiferromagnets. Using time-resolved X-ray diffraction and optical linear dichroism measurements, interlayer shear is identified as the primary structural degree of freedom that couples with magnetic order. The recovery times of both shear and magnetic order upon optical excitation diverge at the magnetic ordering temperature with the same critical exponent. The time-dependent Ginzburg-Landau theory shows that this concurrent critical slowing down arises from a linear coupling of the interlayer shear to the magnetic order, which is dictated by the broken mirror symmetry intrinsic to the monoclinic stacking. Our results highlight the importance of interlayer shear in ultrafast control of magnetic order via spin-mechanical coupling. Van der Waals materials are characterized by two dimensional layers weakly held together by interlayer van der Waals forces. Here, the authors study how shear motions between these layers influence the magnetic properties of the van der Waals antiferromagnets FePS3, MnPS3, and NiPS3. '

Automated summary

This study reveals the existence of a spin-shear coupling mechanism in van der Waals antiferromagnetic materials, where subtle shear can have a profound effect on magnetic order. Experimental results identify interlayer shear as the primary structural degree of freedom that couples with magnetic order, allowing for ultrafast control of magnetic order through spin-mechanical coupling.