Infrared fingerprints of natural 2D talc and plasmon-phonon coupling in graphene-talc heterostructures
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Universidade Federal de Minas Gerais
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Two-dimensional (2D) materials occupy a noteworthy place in nanophotonics providing for subwavelength light confinement and optical phenomena dissimilar to those of their bulk counterparts. In the mid-infrared, graphenebased heterostructures and van der Waals crystals of hexagonal boron nitride (hBN) overwhelmingly concentrate the attention by exhibiting real-space nano-optics features from plasmons, phonon−polaritons, and hybrid plasmon phonon−polaritons. Here we present a prime study on mid-infrared nanophotonics of talc, a natural atomically flat layered material, and graphene-talc (G-talc) heterostructures using broadband synchrotron infrared nanospectroscopy. Wavelength tuning of the talc vibrational resonances, assigned to in- and out-of-plane molecular vibrations, are achieved by changing the thickness of the crystals, which configures a tunable infrared signature for the 2D talc. In G-talc nanostructures, we unveil a coupling of the graphene plasmons polaritons with surface phonons polaritons of talc, originating hybrid surface plasmon−phonon polaritons modes. In analogy to G-hBN and G-SiO2 heterostructures, the coupling in G-talc produces a large increase in the optovibrational activity for the out-of-plane mode as well as it induces a blue-shift for the in-plane mode. Moreover, the coupling can be modulated by an external gate voltage to the heterostructure when mounted in a transistor configuration. Therefore, our results introduce talc and G-talc heterostructures as appealing materials for nanophotonics, especially for applications involving long wavelengths and active electric tuning of opto-vibrational activity.
Abstract
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Infravermelho, Síncrotron, Plasmons, Nanofotônica
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Soapstone mine, Synchrotron IR nanospectroscopy, Plasmonics, Two-dimensional materials, Gate-tunability, Nanophotonics
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https://pubs.acs.org/doi/10.1021/acsphotonics.7b01017