Ultra-confined plasmons reveal moiré patterns in a twisted bilayer graphene–talc heterostructure

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This work investigates the plasmonic properties of a twisted bilayer graphene (TBG) and talc heterostructure. Talc, a naturally occurring phyllosilicate, promotes p-type charging of graphene, supporting high charge mobility and strong interaction between graphene plasmons and talc's phonon polaritons. This interaction results in the formation of surface plasmon-phonon polariton (SP3) modes, which are detected using infrared scattering-type scanning near-field optical microscopy (IR s-SNOM) at room temperature. Notably, without the need for electrostatic gating, our study reveals confinement of SP3 modes in a TBG-talc heterostructure and a transition from surface plasmonic waves to the emergence of moiré superlattices, characterized by reflections at domain walls. These findings provide fresh insights into the coupling mechanisms in hybrid materials and suggest promising applications in nanoscale optoelectronics.