Observation of hyperbolic intersubband polaritons in native-dielectric-doped van der Waals semiconductor quantum wells

Yue Luo; Dapeng Ding; Andres M. Mier Valdivia; Daniel T. Larson; Song Liu; Hong Kuan Ng; Jing Wu; Kenji Watanabe; Takashi Taniguchi; Efthimios Kaxiras; Hongkun Park; Philip Kim; William L. Wilson

doi:10.1038/s41467-025-65196-y

Journal article Observation of hyperbolic intersubband polaritons in native-dielectric-doped van der Waals semiconductor quantum wells

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Yue Luo, Dapeng Ding, Andres M. Mier Valdivia, Daniel T. Larson, Song Liu, Hong Kuan Ng, Jing Wu, Kenji Watanabe, Takashi Taniguchi, Efthimios Kaxiras, Hongkun Park, Philip Kim, William L. Wilson. Observation of hyperbolic intersubband polaritons in native-dielectric-doped van der Waals semiconductor quantum wells. Nature Communications. 2025, 16 (1), 10158. https://doi.org/10.1038/s41467-025-65196-y

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Highly doped semiconductor quantum wells (QWs) exhibit strong intersubband transitions resulting from the nanoscale confinement of electrons. The coupling of photons to these collective electronic dipoles in this anisotropic quantum structure enables intersubband polaritons with a strong nonlinear optical response and hyperbolicity. Analogous to the well-established epitaxially grown multi-quantum wells, two-dimensional (2D) van der Waals (vdW) semiconductor heterostructures provide a compelling alternative platform for this phenomenon, offering an additional degree of freedom and exceptional optoelectronic properties Here we report the realization of intersubband polaritons in multilayer vdW QWs with broadband tunability across the mid-infrared, from 98 to 270 meV. By engineering the top layer of WSe₂ into a self-limiting native oxide, we activate charge transfer that enables controlled high-density doping. This doping regime allows strong intersubband transitions and the emergence of polaritonic behavior, which we directly visualize through their dispersive propagation. Lithographically defined nanostructures further reveal the hyperbolic nature of these polaritons, enabling sub-diffractional confinement in resonant geometries. Moreover, we demonstrate electrical tunability via electrostatic gating, offering dynamic control over polaritonic dispersion. These results position vdW quantum wells as a highly adaptable materials platform for tunable mid-infrared nanophotonics, with potential applications in integrated polaritonic circuits, photodetectors, and light sources.

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