Giant Magneto-Exciton Coupling in 2D van der Waals CrSBr

TL;DR

This study demonstrates strong magneto-exciton coupling in 2D CrSBr, revealing how magnetic order influences exciton behavior and enabling potential applications in spintronics and quantum communication.

Contribution

It uncovers the robust coupling between magnetic order and excitons in 2D CrSBr, with experimental and theoretical insights into exciton energy shifts during magnetic transitions.

Findings

Magnetic order can be switched with a 0.425T in-plane magnetic field.

Exciton energy shifts up to 32 meV during magnetic transitions.

Strong exciton-magnetic order coupling persists at 80 K.

Abstract

Controlling magnetic order via external fields or heterostructures enables precise manipulation and tracking of spin and exciton information, facilitating the development of high-performance optical spin valves. However, the weak magneto-optical signals and instability of two dimensional (2D) antiferromagnetic (AFM) materials have hindered comprehensive studies on the complex coupling between magnetic order and excitons in bulk-like systems. Here, we leverage magneto-optical spectroscopy to reveal the impact of magnetic order on exciton-phonon coupling and exciton-magnetic order coupling which remains robust even under non-extreme temperature conditions (80 K) in thick layered CrSBr. A 0.425T in-plane magnetic field is sufficient to induce spin flipping and transition from AFM to ferromagnetic (FM) magnetic order in CrSBr, while magnetic circular dichroism (MCD) spectroscopy under an out-of-plane magnetic field provides direct insight into the complex spin canting behavior in thicker layers. Theoretical calculations reveal that the strong coupling between excitons and magnetic order, especially the 32 meV exciton energy shift during magnetic transitions, stems from the hybridization of Cr and S orbitals and the larger exciton wavefunction radius of higher-energy B excitons. These findings offer new opportunities and a solid foundation for future exploration of 2D AFM materials in magneto-optical sensors and quantum communication using excitons as spin carriers.