Physical Review Letters· 2026Q1
Microscopic theory of phonon polaritons and long-wavelength dielectric response
- 2citations
- Q1SCImago
- 2026year
Short summary
A first-principles theory accurately calculates phonon-polariton dispersion, resolving ambiguities in dielectric response, especially for anisotropic materials, by quantizing a Hamiltonian that couples lattice vibrations and the electromagnetic field.
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Key points
- Presents a first-principles approach for calculating phonon-polariton dispersion relations.
- Quantizes a Hamiltonian coupling lattice vibrations and the electromagnetic field.
- Naturally includes retardation effects and resolves non-analytical behavior at the Brillouin zone center.
- Accounts for quasiparticle interactions and spectral broadening via higher-order terms.
- Demonstrates the approach on GaP, GaN, PbTe, and $β$-Ga$_2$O$_3$.
AI-generated from the title and abstract; the full text is not read.
Abstract
We present a first-principles approach for calculating phonon-polariton dispersion relations. In this approach, phonon-photon interaction is described by quantization of a Hamiltonian that describes harmonic lattice vibrations coupled with the electromagnetic field inside the material. All Hamiltonian parameters are obtained from first-principles calculations, with diagonalization leading to non-interacting polariton quasiparticles. This method naturally includes retardation effects and resolves non-analytical behavior and ambiguities in phonon frequencies at the Brillouin zone center, especially in non-cubic and optically anisotropic materials. Furthermore, by incorporating higher-order terms in the Hamiltonian, we also account for quasiparticle interactions and spectral broadening. Specifically, we show how anharmonic effects in phonon polaritons lead to a dielectric response that challenges traditional models. The accuracy and consequences of the approach are demonstrated on GaP and GaN as harmonic test systems and PbTe and $β$-Ga$_2$O$_3$ as anharmonic test systems.
The authors' abstract, as published at the source. Physical Review Letters, 2026 · DOI ↗
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