Ultrabroadband and Reversible Tuning of Infrared Plasmons in van der Waals Metal Films.

Reconfigurable infrared plasmons are central to emerging nanophotonic technologies, yet their practical impact remains constrained by limited tuning bandwidth, poor reversibility, and material-specific spectral windows. Here we demonstrate ultrabroadband and fully reversible tuning of infrared plasmons in metallic van der Waals NbSe2 films enabled by gate-controlled lithium-ion intercalation. Ion intercalation provides a unique pathway to simultaneously modulate free-carrier density and screening from high-energy interband transitions, jointly reshaping both plasmon frequency and oscillator strength. As a result, plasmon resonances can be continuously swept over an unprecedented spectral span exceeding 5500 cm-1 within a single material platform, covering the telecom, mid-infrared and thermal far-infrared region. Leveraging this broad and reversible tunability, we realize electrically tunable wavelength-selective thermal emitters and thermal display patterns through plasmon-mediated emissivity modulation. Our results establish ion-intercalated van der Waals metals as a versatile and programmable platform for ultrabroadband tunable infrared nanophotonics and reversible thermal-radiation control.