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arXiv · 2512.17647

Hyperbolic-enhanced Raman scattering in van der Waals MoOCl2: from Fano resonances to picomolar detection

Anton Minnekhanov·Gleb Tikhonowski·Georgy Ermolaev·Konstantin V. Kravtsov·Gleb Tselikov·Adilet Toksumakov·Aleksandr Slavich·Ivan Kazantsev·Ilia Fradkin·Andrey Vyshnevyy·Ivan Kruglov·Ilya Radko·Zdenek Sofer·Aleksey Arsenin·Kostya S. Novoselov·Valentyn Volkov
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Abstract

Natural van der Waals (vdW) crystals with hyperbolic dispersion challenge artificial metamaterials but remain confined to the mid-infrared. The emergence of MoOCl2, a quasi-one-dimensional metal with in-plane hyperbolicity, overcomes this spectral limit, shifting the focus to the practical visible range. Here, using angle-resolved polarized Raman spectroscopy, we uncover pronounced polarization-dependent Fano lineshapes that reveal coupling between phonons and the anisotropic metallic continuum, together with strong wavelength-dependent reshaping of the Raman polarization patterns governed by the anisotropic optical response of MoOCl2. Harnessing this optical anisotropy, we demonstrate "Hyperbolic-Enhanced Raman" (HypER) scattering, where MoOCl2 provides polarization-tunable analytical enhancement factors exceeding 10^7 and picomolar-level detection of Rhodamine 6G down to 100 pM, without deliberate surface nanostructuring. These results establish air-stable MoOCl2 as a simple, wafer-compatible platform for visible-range hyperbolic nanophotonics and lithography-free sensing.

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Anton Minnekhanov, Gleb Tikhonowski, Georgy Ermolaev, Konstantin V. Kravtsov, Gleb Tselikov, Adilet Toksumakov, Aleksandr Slavich, Ivan Kazantsev, Ilia Fradkin, Andrey Vyshnevyy, Ivan Kruglov, Ilya Radko, Zdenek Sofer, Aleksey Arsenin, Kostya S. Novoselov, Valentyn Volkov. 2025-12-19. Hyperbolic-enhanced Raman scattering in van der Waals MoOCl2: from Fano resonances to picomolar detection. https://arxiv.org/abs/2512.17647

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