Tailoring Phonon Polaritons in hBN with the Plasmonic Phase-Change Material In<sub>3</sub>SbTe<sub>2</sub>.

Jäckering, Lina; Moos, Aaron; Conrads, Lukas; Li, Yiheng; Rothstein, Alexander; Malik, Dominique; Watanabe, Kenji; Taniguchi, Takashi et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

Polaritons in van-der-Waals materials (vdWMs) promise high confinement and multiple tailoring options by resonators and launching structures which conventionally require cumbersome lithography techniques. Optical programming of phase-change materials (PCMs) offers fast and reconfigurable fabrication of these structures. As the plasmonic PCM In<sub>3</sub>SbTe<sub>2</sub> can be switched between a dielectric and metallic phase, In<sub>3</sub>SbTe<sub>2</sub> is promising for optical programming of metallic launching structures to tailor and confine polaritons in vdWMs. Here, we combine the vdWM hexagonal boron nitride (hBN) with In<sub>3</sub>SbTe<sub>2</sub> and optically program circular resonators for hBN's phonon polaritons into In<sub>3</sub>SbTe<sub>2</sub>. We investigate the polariton resonators with near-field optical microscopy. Demonstrating the reconfigurability, we decrease the resonator diameter to increase the confinement up to λ/39 and achieve a quality factor of 72. Finally, we fabricate a focusing structure for hBN's polaritons whose focal point we reconfigure. We promote In<sub>3</sub>SbTe<sub>2</sub> as a versatile platform for rapid prototyping of polariton optics in vdWMs.