Polariton spectroscopy at the diamond K-edge via X-ray parametric down-conversion

Fridtjof Kerker; Dietrich Krebs; Xenia Brockmüller; Ankita Negi; Christoph J. Sahle; Blanka Detlefs; Christina Boemer

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arXiv · 2606.02619

Polariton spectroscopy at the diamond K-edge via X-ray parametric down-conversion

Fridtjof Kerker·Dietrich Krebs·Xenia Brockmüller·Ankita Negi·Christoph J. Sahle·Blanka Detlefs·Christina Boemer

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Abstract

It has recently been shown that x-ray parametric down-conversion (XPDC) provides access to high-energy polaritons, resulting from the hybridization of down-converted photons with electronic excitations in a nonlinear medium. Here, we present a spectrally resolved study of this effect around the K-shell absorption edge in diamond. Our results exhibit pronounced signatures of polaritonic hybridization, which we visualize by introducing a polariton spectral map and analyze by help of theoretical modelling. We find that the hybridization at this absorption edge results in substantially higher coupling strength than previously reported for a non-resonant case and reaches well into the strong-coupling regime. In addition, we demonstrate how our measurements of polaritonic XPDC allow us to extract the refractive index for bulk diamond at high spectral resolution around the carbon K-edge.

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Fridtjof Kerker, Dietrich Krebs, Xenia Brockmüller, Ankita Negi, Christoph J. Sahle, Blanka Detlefs, Christina Boemer. 2026-05-27. Polariton spectroscopy at the diamond K-edge via X-ray parametric down-conversion. https://arxiv.org/abs/2606.02619

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