Raman Spectroscopy of Twisted Double Bilayer CrI3 Moiré Superlattices and Nematicity in 2D XY-Type Magnet NiPS3

Two-dimensional (2D) materials with intrinsic ferromagnetism/antiferromagnetism have attracted strong interest because of their potential applications in data storage and spintronic devices. In the first part of this talk, I will present our magneto-Raman and magnetic circular dichroism (MCD) spectroscopy studies of twisted double bilayer (tDB) CrI₃. We identify Raman signatures of a new magnetic ground state that is distinct from those in natural two-layer (2L) and four-layer (4L) CrI₃. Results from Raman and MCD both reveal the emergence of finite net magnetization that originates from spin frustrations and noncollinear spin texture introduced by moiré superstructures in tDB CrI₃. In the second part of this talk, I will show our studies of spin-induced nematicity in few-layer XY-type magnet NiPS₃. Our findings suggest that spin fluctuations in few-layer NiPS₃ at low temperature are so strong that they destroy the static, long-range antiferromagnetic order for 3D, but instead, introduce a nematic state in 2D NiPS₃. Our studies offer an unprecedented venue for realizing novel magnetic states and phases in 2D magnets.<br/><br/>Funded by NSF Grant No. DMR-2104036 and NSF CAREER Grant No. DMR-1760668.