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While most approaches to polariton research focus on achieving strong coupling between excitons in monolayer transition metal dichalcogenides (TMDCs) and external microcavities, bulk TMDCs have been largely overlooked due to their reduced exciton oscillator strength and indirect bandgap nature. Here, we report the observation of polariton condensation within the indirect-transition range, enabled by a condensation mechanism in 50-nm-thick WS₂-based bound state in the continuum (BIC) cavities. Our photonic-like BIC polaritons exhibit a significant Rabi splitting energy ( ~ 294 meV) and clear evidence of condensation driven by a mechanism involving indirect excitons that directly inject photons into BIC polaritons. Remarkably, the interaction-induced confinement of polariton condensates can be optically tuned by adjusting the pump laser size, despite a minimal exciton fraction of 6%, distinguishing this system from purely photonic counterparts. These findings open new avenues for exploring polariton physics with indirect excitons in TMDCs and other emerging materials.

Abstract Electrolyte‐gated organic synaptic transistors (EGOSTs) are promising candidates for next‐generation neuromorphic devices due to their low‐power operation, tunable conductance, and fast response from ion transport. To realize EGOSTs using conventional organic solvent electrolytes, issues such as unstable electric double layer (EDL) formation and rapid depolarization often arise, resulting in poor ion retention and limited non‐volatile performance. In contrast, aqueous electrolytes offer high electrochemical stability, an eco‐friendly process, and biocompatibility. However, strategies to precisely regulate ion dynamics in aqueous systems remain insufficiently developed. Here, a zwitterion electrolyte design based on electrostatic inter‐ion repulsion is proposed to enhance non‐volatile characteristics in aqueous systems. By introducing a symmetrical charge‐pair structure into the [Li‐TFSI] electrolyte, it is demonstrated that ion back‐diffusion can be suppressed, and stable EDL formation maintained, as confirmed by electrochemical impedance spectroscopy, cyclic voltammetry, UV–vis absorption, and real‐time FT‐IR analysis. The fabricated EGOSTs implement stable synaptic characteristics, including enhanced long‐term plasticity and potentiation/depression. Furthermore, artificial neural network simulations using a modified National Institute of Standards and Technology (MNIST) handwritten digit dataset demonstrate a recognition accuracy of 94.88%. These findings provide valuable insights into electrolyte design strategies for stable and efficient neuromorphic devices through the control of inter‐ion interactions.

Abstract Efficient guiding and manipulation of photons at the nanoscale is essential for optical communication and computing. Recent studies have demonstrated that atomically thin 2D semiconductors can function as waveguides even at atomic‐scale thickness, also enabling optical modulation. However, electrical control over guided modes in these atomically thin 2D semiconductors remains largely unexplored. In this report, electrical modulation of guided exciton‐polariton modes within a van der Waals heterostructure composed of an atomically thin tungsten disulfide (WS 2 ) monolayer integrated with hexagonal boron nitride (hBN) is demonstrated. Due to the electrostatic tunability of excitons in monolayer WS 2 , the guided polariton modes in the WS 2 /hBN heterostructure can be electrically modulated. The polariton dispersions in this heterostructure are directly observed under varying gate voltage by using the near‐field coupling technique. Remarkably, the polariton dispersion can be switched off by applying an electrostatic gate voltage of 30 V to optically transparent indium tin oxide (ITO) electrodes. It is believed that this work provides a promising platform for nanoscale polaritonic devices and their integration into on‐chip applications.