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Vacancy-Engineered Phonon Polaritons in a van der Waals Crystal
Mashnoon Alam Sakib1, Naveed Hussain1, Mariia Stepanova1
1Department of Electrical Engineering and Computer Science, University of California, Irvine, California 92697, United States.
ACS Nano
|May 15, 2026
Summary
We demonstrate a new thermomechanical method to tune phonon polaritons (PhPs) in van der Waals materials. This approach uses oxygen vacancies and strain to reconfigure light-matter interactions for nanophotonics.
Area of Science:
- Condensed Matter Physics
- Nanophotonics
- Materials Science
Background:
- Phonon polaritons (PhPs) in low-symmetry van der Waals (vdW) materials offer deep-subwavelength control of mid-infrared light.
- Reconfiguring PhPs intrinsically without external fields or complex fabrication remains a challenge.
Purpose of the Study:
- To introduce and validate a thermomechanical approach for tuning PhPs in α-molybdenum trioxide (α-MoO3).
- To achieve intrinsic reconfiguration of polariton dispersion through controlled oxygen vacancy formation and lattice strain.
Main Methods:
- Near-field nanoimaging to observe polariton wavevector shifts.
- Stoichiometric analysis and density functional theory (DFT) to understand material changes.
- Finite-difference time-domain (FDTD) simulations for optical response analysis.
Main Results:
- An average polariton wavevector shift of Δk/k ≈ 0.13 was observed.
- Controlled oxygen vacancy formation (1-2%) and compressive strain (≈-1.2%) were achieved.
- Significant dielectric permittivity modulation (up to ≈15%) with sustained polariton lifetimes (1.15 ± 0.29 ps).
Conclusions:
- Thermomechanical vacancy engineering provides a robust method for tuning PhPs in vdW materials.
- This technique enables reprogrammable polaritonic responses for nonvolatile nanophotonic devices.
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