Stacking dependent magnetism in van der Waals magnets

In recent years it has become increasingly clear that stacking engineering in van der Waals materials can be a powerful tool to realize novel properties and functionalities. In this talk, I will discuss stacking dependent magnetism in van der Waals magnets, using bilayer CrI₃ as an example. I will first show that a relative shift between the two layers at the fraction of the lattice constant can lead to drastic change in the magnetic states. As a result, stacking domain walls can host one dimensional magnon channels, which have lower energies than bulk magnons. Interestingly, some magnon channels are hidden in magnetically homogeneous background. In a moire superlattice, these 1D magnon channels form an interconnected network, which will dominate low-energy spin and thermal transport. These results reveal the importance of stacking domain walls in understanding magnetic properties of van der Waals magnets, and extend the scope of stacking engineering to magnetic dynamics.