Whirling interlayer fields as a new source of stable topological order in moiré CrI3

Abstract

The moiré engineering of two-dimensional magnets opens unprecedented opportunities to design novel magnetic states via the stacking-dependent magnetism. Here, we explore the formation and control of ground state topological spin structures (TSTs) in moiré CrI3 without including the nearest-neighbor (NN) Dzyaloshinskii-Moriya interactions (DMI) and dipolar interactions in the theoretical approach. Using stochastic Landau-Lifshitz-Gilbert simulations, we unveil the emergence of vortex and antivortex interlayer exchange fields at large moiré periodicity. The whirling fields stabilize spontaneous and field-assisted ground state TSTs with various topologies, including skyrmionic clusters with high topological charges. Furthermore, by examining the effect of the Kitaev interaction and the next NN DMI, we propose the latter as the unique spin-orbit coupling mechanism compatible with the experimental results on monolayer and twisted CrI3. Therefore, our study goes beyond the current knowledge about TSTs in moiré magnets, opens exciting opportunities for moiré skyrmionics, and uncovers the spin-orbit coupling in CrI3.

Domain Wall Formation and Magnon Localization in Twisted Chromium Trihalides

“…In contrast, the formation of noncollinear phases and skyrmions in chromium trihalides have been recently predicted using stochastic Landau–Lifshitz–Gilbert simulations and DFT calculations. [ 27–29 ] In presence of spin‐orbit coupling, layered structures with broken inversion symmetry can give rise to an antisymmetric exchange anisotropy, also known as Dzyaloshinskii–Moriya interaction (DMI). Recent experiments have observed the formation of spin spirals in the surface of Fe 3 GeTe 2 induced by the strong DMI.…”

Prediction of Magnetic Skyrmions in A New Kind of Twisted Bilayer CrI$_3$

“…The magnetic state of a CrI 3 bilayer can be tuned by electric field [15][16][17][18], external pressure [19][20][21][22], and charge doping [23][24][25]. Theoretical studies have predicted that it also depends on the stacking structure [26][27][28], and a twisting may bring periodic magnetization domains with complex spin texture [29][30][31]; additional Dzyaloshinskii-Moriya (DM) interactions may further stabilize various magnetic skyrmions [32][33][34][35]. Compared with magnetic skyrmions in alloys [36][37][38], the magnetic skyrmions in TBCIs are much thinner, they reach the two-dimensional limit, and open up the field of spintwistronics [39].…”