Vertical plasmonic coupling in double-layer graphene leads to two hybridized plasmonic modes: the optical and the acoustic plasmon with symmetric and antisymmetric charge distributions across the interlayer gap, respectively. However, in most experiments based on far-field excitation, only the optical plasmon are dominantly excited in the double-layer graphene systems. Here, we propose strategies to selectively and efficiently excite the acoustic plasmon with single or multiple nanoemitters. The analytical model developed here elucidates the role of the position and arrangement of the emitters on the symmetry of the resulting graphene plasmons. In addition, we present an optimal device structure to enable an experimental observation of the acoustic plasmon in double-layer graphene toward the ultimate level of plasmonic confinement defined by a monoatomic spacer, which is inaccessible with a graphene-on-a-mirror architecture.
Bibliographical noteFunding Information:
This research is supported by grants from the National Science Foundation (NSF) MRSEC Seed (to I.-H.L., T.L., and S.-H.O.), NSF ECCS Award No. 1809723 (to I.-H.L., S.-H.O., T.L.), NSF CCSS Award No. 2227460 (to S.-H.O.), and the Samsung Global Research Outreach (GRO) Program (to S.-H.O.). I.-H.L. acknowledges financial support from the Korea Institute of Science and Technology (KIST) Institutional Program (Grant No. 2E32242) and the National Research Foundation of Korea (Grant No. RS-2023-00211359). L.M.-M acknowledges Project PID2020-115221GB-C41, financed by MCIN/AEI/10.13039/501100011033, funding from the European Union Seventh Framework Programme under Grant Agreement No. 881603 Graphene Flagship for Core3, and the Aragon Government through Project Q-MAD. S.-H.O. further acknowledges support from the Sanford P. Bordeau Chair at the University of Minnesota.
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