Two-dimensional (2D) magnetic semiconductors feature both tightly-bound excitons with large oscillator strength and potentially long-lived coherent magnons due to the presence of bandgap and spatial confinement. While magnons and excitons are energetically mismatched by orders of magnitude, their coupling can lead to efficient optical access to spin information. Here we report strong magnon-exciton coupling in the 2D van der Waals (vdW) antiferromagnetic (AFM) semiconductor CrSBr. Coherent magnons launched by above-gap excitation modulate the interlayer hybridization, which leads to dynamic modulation of excitonic energies. Time-resolved exciton sensing reveals magnons that can coherently travel beyond 7 micrometer, with coherence time above 5 ns. We observe this exciton-coupled coherent magnons in both even and odd number of layers, with and without compensated magnetization, down to the bilayer limit. Given the versatility of vdW heterostructures, these coherent 2D magnons may be basis for optically accessible magnonics and quantum interconnects.
@article{arxiv.2201.13197,
title = {Exciton-Coupled Coherent Magnons in a 2D Semiconductor},
author = {Youn Jue Bae and Jue Wang and Allen Scheie and Junwen Xu and Daniel G. Chica and Geoffrey M. Diederich and John Cenker and Michael E. Ziebel and Yusong Bai and Haowen Ren and Cory R. Dean and Milan Delor and Xiaodong Xu and Xavier Roy and Andrew D. Kent and Xiaoyang Zhu},
journal= {arXiv preprint arXiv:2201.13197},
year = {2022}
}