Cavity-driven attractive interactions in quantum materials.
basic_science · Level V
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- Record sourced from PubMed, PMID 42203865.
- Also identified by DOI 10.1038/s41586-026-10609-1.
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Abstract
Many-body phenomena in quantum materials emerge from the interplay among a broad continuum of electronic states and controlling these interactions is critical for engineering new phases. One promising approach exploits light confined within optical cavities to tailor electronic properties<sup>1</sup>. Here we demonstrate that terahertz cavity photons can mediate attractive interactions in a tunable van der Waals (vdW) material and reorganize a continuum of electron-hole transitions into an exciton-like state. We introduce a broadband, sub-wavelength time-domain microscope that integrates exfoliated, dual-gated 2D quantum materials into a terahertz cavity. This approach enables the spectroscopic measurement of the field-tunable bandgap of bilayer graphene<sup>2</sup> (BLG) in the terahertz range and, at resonance, reveals ultrastrong coupling<sup>3</sup> (USC) with an effective interaction strength exceeding g/ω<sub>c</sub> ≈ 40% of the bare photon energy. Crucially, we identify a cavity-induced resonance emerging from the interband continuum that resembles Coulomb-bound excitons and remains stable across a broad temperature range. Our findings propose an experimental platform for designing and investigating hybrid light-matter phases in 2D quantum matter.