DOE OSTI · 2529421
Magnetically confined surface and bulk excitons in a layered antiferromagnet
Abstract
The discovery of two-dimensional van der Waals magnets has greatly expanded our ability to create and control nanoscale quantum phases. A unique capability emerges when a two-dimensional magnet is also a semiconductor that features tightly bound excitons with large oscillator strengths that fundamentally determine the optical response and are tunable with magnetic fields. Here, in this study, we report a previously unidentified type of optical excitation-a magnetic surface exciton-enabled by the antiferromagnetic spin correlations that confine excitons to the surface of CrSBr. Magnetic surface excitons exhibit stronger Coulomb attraction, leading to a higher binding energy than excitons confined in bulk layers, and profoundly alter the optical response of few-layer crystals. Distinct magnetic confinement of surface and bulk excitons is established by layer- and temperature-dependent exciton reflection spectroscopy and corroborated by ab initio many-body perturbation theory calculations. By quenching interlayer excitonic interactions, the antiferromagnetic order of CrSBr strictly confines the bound electron-hole pairs within the same layer, regardless of the total number of layers. Our work unveils unique confined excitons in a layered antiferromagnet, highlighting magnetic interactions as a vital approach for nanoscale quantum confinement, from few layers to the bulk limit.
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Shao, Yinming [Columbia University, New York, NY (United States); Pennsylvania State University, University Park, PA (United States)] (ORCID:0000000228910028), Dirnberger, Florian [Technische Universität Dresden (Germany); Technical University of Munich (Germany); Technical University of Munich, Garching (Germany)] (ORCID:0000000229322850), Qiu, Siyuan [Columbia University, New York, NY (United States)], Acharya, Swagata [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000180740030), Terres, Sophia [Technische Universität Dresden (Germany)], Telford, Evan J. [Columbia University, New York, NY (United States)] (ORCID:0000000294949166), Pashov, Dimitar [King's College, London (United Kingdom)] (ORCID:0000000242929745), Kim, Brian S. Y. [Columbia University, New York, NY (United States); University of Arizona, Tucson, AZ (United States)] (ORCID:0000000230244220), Ruta, Francesco L. [Columbia University, New York, NY (United States)] (ORCID:0000000287469420), Chica, Daniel G. [Columbia University, New York, NY (United States)], Dismukes, Avalon H. [Columbia University, New York, NY (United States)], Ziebel, Michael E. [Columbia University, New York, NY (United States)] (ORCID:0000000318578292), Wang, Yiping [Columbia University, New York, NY (United States)] (ORCID:0000000315760785), Choe, Jeongheon [Columbia University, New York, NY (United States)] (ORCID:0000000292721133), Bae, Youn Jue [Columbia University, New York, NY (United States)], Millis, Andrew J. [Columbia University, New York, NY (United States); Flatiron Institute, New York, NY (United States)] (ORCID:0000000194136344), Katsnelson, Mikhail I. [Radboud University, Nijmegen (Netherlands)] (ORCID:0000000151657553), Mosina, Kseniia [University of Chemistry and Technology Prague (Czech Republic)], Sofer, Zdenek [University of Chemistry and Technology Prague (Czech Republic)] (ORCID:0000000213914448), Huber, Rupert [University of Regensburg (Germany)] (ORCID:0000000166179283), Zhu, Xiaoyang [Columbia University, New York, NY (United States)] (ORCID:0000000220908484), Roy, Xavier [Columbia University, New York, NY (United States)] (ORCID:0000000288500725), van Schilfgaarde, Mark [National Renewable Energy Laboratory (NREL), Golden, CO (United States)] (ORCID:0000000312104459), Chernikov, Alexey [Technische Universität Dresden (Germany)], Basov, D. N. [Columbia University, New York, NY (United States)] (ORCID:0000000197855387). 2025-02-19. Magnetically confined surface and bulk excitons in a layered antiferromagnet. https://doi.org/10.1038/s41563-025-02129-6
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