期刊
SCIENCE ADVANCES
卷 5, 期 4, 页码 -出版社
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/sciadv.aau7171
关键词
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资金
- NSF EFRI award [1542807]
- NSF [1541959]
- Swiss National Science Foundation (SNSF) [168545, 177836]
- Science and Technology Center for Integrated Quantum Materials, NSF [DMR-1231319]
Van der Waals (vdW) heterostructures assembled from layers of two-dimensional materials have attracted considerable interest due to their novel optical and electrical properties. Here, we report a scattering-type scanning near-field opticalmicroscopy study of hexagonal boron nitride on black phosphorus (h-BN/BP) heterostructures, demonstrating the first direct observation of in-plane anisotropic phonon polariton modes in vdW heterostructures. Notably, the measured in-plane optical anisotropy along the armchair and zigzag crystal axes exceeds the ratio of refractive indices of BP in the x-y plane. We explain that this enhancement is due to the high confinement of the phonon polaritons in h-BN. We observe a maximum in-plane optical anisotropy of alpha(max) = 1.25 in the frequency spectrum at 1405 to 1440 cm(-1). These results provide new insights into the behavior of polaritons in vdW heterostructures, and the observed anisotropy enhancement paves the way to novel nanophotonic devices and to a new way to characterize optical anisotropy in thin films.
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