Multiferroic-enabled magnetic exciton in 2D quantum entangled van der Waals antiferromagnet NiI2

TL;DR

This paper demonstrates that multiferroicity-induced inversion symmetry breaking enables magnetic excitons in 2D NiI2, arising from quantum entangled states, with potential for controlling matter-light interactions in quantum materials.

Contribution

It reveals that multiferroicity controls magnetic excitons in 2D NiI2 through quantum entanglement, a novel mechanism in van der Waals antiferromagnets.

Findings

Magnetic exciton in NiI2 is controlled by multiferroicity.

The exciton originates from quantum entangled Zhang-Rice states.

An ultra-sharp optical exciton peak at 1.384 eV was observed.

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, we report that the broken inversion symmetry of multiferroicity can act as an external knob enabling the magnetic exciton in van der Waals antiferromagnet NiI2. We further discover that this magnetic exciton arises from a transition between Zhang-Rice-triplet and Zhang-Rice-singlet's fundamentally quantum entangled states. This quantum entanglement produces an ultra-sharp optical exciton peak at 1.384 eV with a 5 meV linewidth. Our work demonstrates that NiI2 is two-dimensional magnetically ordered with an intrinsically quantum entangled ground state.