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arXiv · 2109.02800

Near-field probing of image phonon-polaritons in hexagonal boron nitride on gold crystals

Sergey G. Menabde·Sergejs Boroviks·Jongtae Ahn·Jacob T. Heiden·Kenji Watanabe·Takashi Taniguchi·Tony Low·Do Kyung Hwang·N. Asger Mortensen·Min Seok Jang
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Abstract

Near-field mapping has been widely used to study hyperbolic phonon-polaritons in van der Waals crystals. However, an accurate measurement of the polaritonic loss remains challenging because of the inherent complexity of the near-field signal and the substrate-mediated loss. Here we demonstrate that large-area monocrystalline gold flakes, an atomically-flat low-loss substrate for image polaritons, provide a platform for precise near-field measurement of the complex propagation constant of polaritons in van der Waals crystals. As a topical example, we measure propagation loss of the image phonon-polaritons in hexagonal boron nitride, revealing that their normalized propagation length exhibits a parabolic spectral dependency. Further, we show that image phonon-polaritons exhibit up to a twice lower normalized propagation loss, while being 2.4 times more compressed compared to the case of dielectric substrate. We conclude that the monocrystalline gold flakes provide a unique nanophotonic platform for probing and exploitation of the image modes in low-dimensional materials.

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Sergey G. Menabde, Sergejs Boroviks, Jongtae Ahn, Jacob T. Heiden, Kenji Watanabe, Takashi Taniguchi, Tony Low, Do Kyung Hwang, N. Asger Mortensen, Min Seok Jang. 2021-09-07. Near-field probing of image phonon-polaritons in hexagonal boron nitride on gold crystals. https://doi.org/10.1126/sciadv.abn0627

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