Tuning two-dimensional magnetism in twisted CrI₃ double bilayers

Twisting two-dimensional (2D) atomic crystals can lead to a plethora of novel emergent electronic and phononic states. Such new states are absent in the constituent natural 2D crystals, which deems twisting as a new and efficient platform for realizing novel 2D phases. Recent discoveries of 2D magnetic atomic crystals open the door to design new magnetic properties via twisting, and indeed, there have been a few theoretical predictions on nontrivial magnetic phases developing in twisted 2D magnets. In this talk, I will show our recent efforts on tuning 2D magnetism by twisting two CrI₃ bilayers and examining them with polarized magneto-Raman spectroscopy. While individual CrI₃ bilayers and any homogeneous stacking of them should have a zero total magnetization, we report our finding that twisted CrI₃ double bilayers at special twist angles around 1.1^o realize an unexpected magnetic state with non-zero total magnetizations. This twist-induced net magnetization is believed to arise from competitions between coexisting ferromagnetic and antiferromagnetic interlayer exchange coupling within individual moiré supercells.