Skyrmions in twisted van der Waals magnets*

Magnetic skyrmions in two-dimensional (2D) chiral magnets are often stabilized by a combination of
Dzyaloshinskii-Moriya interaction and external magnetic field. Here, we show that skyrmions can also be
stabilized in twisted moire superlattices with Dzyaloshinskii-Moriya interaction in the absence of an external
magnetic field. Our setup consists of a 2D ferromagnetic layer twisted on top of an antiferromagnetic substrate.
The coupling between the ferromagnetic layer and the substrate generates an effective alternating exchange
field. We find a large region of skyrmion crystal phase when the length scales of the moire periodicity and
skyrmions are compatible. Unlike chiral magnets under magnetic field, skyrmions in moire superlattices show
enhanced stability for the easy-axis (Ising) anisotropy which can be essential to realize skyrmions since most
van der Waals magnets possess easy-axis anisotropy.