Anisotropic Excitons Reveal Local Spin Chain Directions in a van der Waals Antiferromagnet

• Published in: Advanced materials (Weinheim) Vol. 35; no. 19; pp. e2206585 - n/a
• Main Authors: Kim, Dong Seob, Huang, Di, Guo, Chunhao, Li, Kejun, Rocca, Dario, Gao, Frank Y., Choe, Jeongheon, Lujan, David, Wu, Ting‐Hsuan, Lin, Kung‐Hsuan, Baldini, Edoardo, Yang, Li, Sharma, Shivani, Kalaivanan, Raju, Sankar, Raman, Lee, Shang‐Fan, Ping, Yuan, Li, Xiaoqin
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.05.2023; Wiley Blackwell (John Wiley & Sons)
• Subjects: antiferromagnet; Antiferromagnetism; Chemical analysis; defect; Excitons; Information storage; Magnetic semiconductors; Magnets; Materials science; Neel temperature; Neutron scattering; optical absorption; Photoluminescence; raman scattering; spin chains; van der Waals material; optical absorption; raman scattering; defect; photoluminescence; van der Waals material; antiferromagnet; spin chains
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202206585

A long‐standing pursuit in materials science is to identify suitable magnetic semiconductors for integrated information storage, processing, and transfer. Van der Waals magnets have brought forth new material candidates for this purpose. Recently, sharp exciton resonances in antiferromagnet NiPS3 have been reported to correlate with magnetic order, that is, the exciton photoluminescence intensity diminishes above the Néel temperature. Here, it is found that the polarization of maximal exciton emission rotates locally, revealing three possible spin chain directions. This discovery establishes a new understanding of the antiferromagnet order hidden in previous neutron scattering and optical experiments. Furthermore, defect‐bound states are suggested as an alternative exciton formation mechanism that has yet to be explored in NiPS3. The supporting evidence includes chemical analysis, excitation power, and thickness dependent photoluminescence and first‐principles calculations. This mechanism for exciton formation is also consistent with the presence of strong phonon side bands. This study shows that anisotropic exciton photoluminescence can be used to read out local spin chain directions in antiferromagnets and realize multi‐functional devices via spin‐photon transduction. Recently, sharp exciton resonances in antiferromagnet NiPS3 have been reported to correlate with magnetic order. It is found that the polarization of maximal exciton emission in NiPS3 rotate locally, revealing three possible spin chain directions. This discovery establishes a new understanding of the antiferromagnetic order hidden in previous neutron scattering and optical experiments.