Sign InSign Up

Cavity-driven attractive interactions in quantum materials

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 properties1. 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 graphene2 (BLG) in the terahertz range and, at resonance, reveals ultrastrong coupling3 (USC) with an effective interaction strength exceeding g/ωc ≈ 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.

Access Nature and 54 other Nature Portfolio journals

Get Nature+, our best-value online-access subscription

$32.99 / 30 days

cancel any time

Subscribe to this journal

Receive 52 print issues and online access

$199.00 per year

only $3.83 per issue

Buy this article

  • Purchase on SpringerLink
  • Instant access to the full article PDF.

USD 39.95

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Sub-wavelength terahertz spectroscopy of cavity-induced bound states.
The alternative text for this image may have been generated using AI.
Fig. 2: Gate-tuned transport and terahertz cavity response of BLG.
The alternative text for this image may have been generated using AI.
Fig. 3: Observation of polariton formation.
The alternative text for this image may have been generated using AI.
Fig. 4: Theory.
The alternative text for this image may have been generated using AI.
Fig. 5: Temperature dependence.
The alternative text for this image may have been generated using AI.

Similar content being viewed by others

Data availability

The numerical simulations and measurement datasets underlying the figures in this paper are available from the corresponding author on request. The raw data that support the findings of this article are also available in the ETH Research Collection (https://doi.org/10.3929/ethz-c-000797558).

Code availability

The code used in the theoretical part of this study is available from the corresponding author on request and in the ETH Research Collection (http://doi.org/10.5905/ethz-1007-932).

References

  1. Lu, I.-T. et al. Cavity engineering of solid-state materials without external driving. Adv. Opt. Photonics 17, 441–525 (2025).

    Article  Google Scholar 

  2. Zhang, Y. et al. Direct observation of a widely tunable bandgap in bilayer graphene. Nature 459, 820–823 (2009).

    Article  ADS  CAS  PubMed  Google Scholar 

  3. Kockum, A. F., Miranowicz, A., De Liberato, S., Savasta, S. & Nori, F. Ultrastrong coupling between light and matter. Nat. Rev. Phys. 1, 19–40 (2019).

    Article  Google Scholar 

  4. Disa, A. S., Nova, T. F. & Cavalleri, A. Engineering crystal structures with light. Nat. Phys. 17, 1087–1092 (2021).

    Article  CAS  Google Scholar 

  5. Lu, I. et al. Cavity-enhanced superconductivity in MgB2 from first-principles quantum electrodynamics (QEDFT). Proc. Natl Acad. Sci. USA 121, e2415061121 (2024).

Visit Website