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arXiv · 2312.08476

Enhanced Magnetization by Defect-Assisted Exciton Recombination in Atomically Thin CrCl$_3$

Xin-Yue Zhang·Thomas K. M. Graham·Hyeonhu Bae·Yu-Xuan Wang·Nazar Delegan·Jonghoon Ahn·Zhi-Cheng Wang·Jakub Regner·Kenji Watanabe·Takashi Taniguchi·Minkyung Jung·Zdeněk Sofer·Fazel Tafti·David D. Awschalom·F. Joseph Heremans·Binghai Yan·Brian B. Zhou
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Abstract

Two dimensional (2D) semiconductors present unique opportunities to intertwine optical and magnetic functionalities and to tune these performances through defects and dopants. Here, we integrate exciton pumping into a quantum sensing protocol on nitrogen-vacancy centers in diamond to image the optically-induced transient stray fields in few-layer, antiferromagnetic CrCl$_3$. We discover that exciton recombination enhances the in-plane magnetization of the CrCl$_3$ layers, with a predominant effect in the surface monolayers. Concomitantly, time-resolved photoluminescence measurements reveal that nonradiative exciton recombination intensifies in atomically thin CrCl$_3$ with tightly localized, nearly dipole-forbidden excitons and amplified surface-to-volume ratio. Supported by experiments under controlled surface exposure and density functional theory calculations, we interpret the magnetically enhanced state to result from a defect-assisted Auger recombination that optically activates electron transfer between water vapor related surface impurities and the spin-polarized conduction band. Our work validates defect engineering as a route to enhance intrinsic magnetism in single magnetic layers and opens a novel experimental platform for studying optically-induced, transient magnetism in condensed matter systems.

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Xin-Yue Zhang, Thomas K. M. Graham, Hyeonhu Bae, Yu-Xuan Wang, Nazar Delegan, Jonghoon Ahn, Zhi-Cheng Wang, Jakub Regner, Kenji Watanabe, Takashi Taniguchi, Minkyung Jung, Zdeněk Sofer, Fazel Tafti, David D. Awschalom, F. Joseph Heremans, Binghai Yan, Brian B. Zhou. 2023-12-13. Enhanced Magnetization by Defect-Assisted Exciton Recombination in Atomically Thin CrCl$_3$. https://doi.org/10.1103/physrevmaterials.8.104402

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