Multiferroic‐Enabled Magnetic‐Excitons in 2D Quantum‐Entangled Van der Waals Antiferromagnet NiI<sub>2</sub>
Suhan Son, Youjin Lee, Jae Ha Kim, Jae Ha Kim, Beom Hyun Kim, Chaebin Kim, Woongki Na, Hwiin Ju, Su-Dong Park, Abhishek Nag, Ke‐Jin Zhou, Young‐Woo Son, Hyeong‐Do Kim, Woo‐Suk Noh, Jae‐Hoon Park, Jae‐Hoon Park, Jong Seok Lee, Hyeonsik Cheong, Jae Ha Kim, Jae Hoon Kim, Je‐Geun Park, Je‐Geun Park
Abstract
Abstract Matter–light interaction is at the center of diverse research fields from quantum optics to condensed matter physics, opening new fields like laser physics. A magnetic exciton is one such rare example found in magnetic insulators. However, it is relatively rare to observe that external variables control matter‐light interaction. Here, it is reported that the broken inversion symmetry of multiferroicity can act as an external knob enabling magnetic excitons in the van der Waals antiferromagnet NiI 2 . It is further discovered that this magnetic exciton arises from a transition between Zhang–Rice‐triplet and Zhang–Rice‐singlet fundamentally quantum‐entangled states. This quantum entanglement produces an ultrasharp optical exciton peak at 1.384 eV with a 5 meV linewidth. The work demonstrates that NiI 2 is 2D magnetically ordered with an intrinsically quantum‐entangled ground state.