Giant electrically tunable magnon transport anisotropy in a van der Waals antiferromagnetic insulator

Anisotropy is a manifestation of lowered symmetry in material systems that have profound fundamental and technological implications. For van der Waals magnets, the two-dimensional (2D) nature greatly enhances the effect of in-plane anisotropy. However, electrical manipulation of such anisotropy as well as demonstration of possible applications remains elusive. In particular, in-situ electrical modulation of anisotropy in spin transport, vital for spintronics applications, has yet to be achieved. Here, we realized giant electrically tunable anisotropy in the transport of second harmonic thermal magnons (SHM) in van der Waals anti-ferromagnetic insulator CrPS4 with the application of modest gate current. Theoretical modeling found that 2D anisotropic spin Seebeck effect is the key to the electrical tunability. Making use of such large and tunable anisotropy, we demonstrated multi-bit read-only memories (ROMs) where information is inscribed by the anisotropy of magnon transport in CrPS4. Our result unveils the potential of anisotropic van der Waals magnons for information storage and processing. The anisotropic electrical and optical response of materials has allowed for the development of variety of sensors, memories and other interesting devices. Here, Qi et al turn their attention to the van der Waals antiferromagnetic insulator CrPS4, and demonstrate a very large, electrically tunable anisotropy in magnon transport, and present a multibit read-only memory based on this anisotropy.