DOE OSTI · 3378279
Collective Modes in Multilayer Graphene/𝛼−RuCl 3 Heterostructures
Abstract
Collective modes in multilayer graphene, such as plasmons and phonons, exhibit sensitivity to displacement fields and interlayer coupling, distinguishing them from their counterparts in single-layer graphene. Here, we engineer collective modes in charge-transfer heterostructures composed of multilayer graphene and 𝛼−RuCl 3 . In heterostructures with a single 𝛼−RuCl 3 interface, the charge transfer generates displacement fields up to 7 V/nm at the interface between 𝛼−RuCl 3 and the adjacent graphene layer—the highest value achieved through charge-transfer methods. As a result of the broken inversion symmetry, we discover enhanced nonlinear optical response and modified phonon selection rules. Conversely, we find that multilayer graphene sandwiched between two 𝛼−RuCl 3 flakes causes displacement fields to cancel. There, we achieve carrier densities as high as 8 ×10 13 cm −2 in multilayer graphene and restore the phonon selection rules to their unperturbed state. Meanwhile, we demonstrate that plasmonic properties derive from the depletion of multiple valence bands. As a result of the quasilinear band dispersion, these “Dirac multiband plasmons” are relatively unaffected by displacement fields. On the other hand, the inverted heterostructure sequence—two multilayer graphene sheets encapsulating 𝛼−RuCl 3 —activates significant alteration of the plasmons via interlayer plasmon-plasmon coupling. Hence, multilayer graphene and 𝛼−RuCl 3 heterostructures offer a gate-free platform for engineering collective modes derived from inversion symmetry and interlayer coupling.
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Moore, Samuel L. [Columbia University, New York, NY (United States)] (ORCID:0000000203062624), Sánchez, Miguel Sánchez [Instituto de Ciencia de Materiales de Madrid (Spain)] (ORCID:0000000280672274), Strasbourg, M. C. [Columbia University, New York, NY (United States)] (ORCID:0009000780621075), Shao, Y. [Pennsylvania State University, University Park, PA (United States)] (ORCID:0000000228910028), Pack, J. [Columbia University, New York, NY (United States)] (ORCID:0000000191798668), Wang, Y. [Columbia University, New York, NY (United States)] (ORCID:0000000315760785), Rizzo, D. J. [Columbia University, New York, NY (United States)], Jessen, B. S. [Technical University of Denmark, Lyngby (Denmark)] (ORCID:0000000184536125), Cothrine, Matthew [University of Tennessee, Knoxville, TN (United States)], Mandrus, David G. [University of Tennessee, Knoxville, TN (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)], Taniguchi, Takashi [National Institute for Materials Science, Tsukuba (Japan)], Watanabe, Kenji [National Institute for Materials Science, Tsukuba (Japan)], Burch, K. S. [Boston College, MA (United States)], Dean, C. R. [Columbia University, New York, NY (United States)], Hone, J. [Columbia University, New York, NY (United States)], Fogler, M. [University of California, San Diego, CA (United States)] (ORCID:0000000182397221), Millis, A. J. [Columbia University, New York, NY (United States)] (ORCID:0000000194136344), Rubio, A. [Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany)] (ORCID:0000000320603151), Schuck, P. J. [Columbia University, New York, NY (United States)], Stauber, T. [Instituto de Ciencia de Materiales de Madrid (Spain)] (ORCID:0000000309832420), Basov, D. N. [Columbia University, New York, NY (United States)] (ORCID:0000000197855387). 2025-10-21. Collective Modes in Multilayer Graphene/𝛼−RuCl 3 Heterostructures. https://doi.org/10.1103/rp3q-svws
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