Journal
NANO LETTERS
Volume -, Issue -, Pages -Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.2c02879
Keywords
phonon polariton; boron nitride; folding edges; electron energy-loss spectroscopy; phonon hardening
Categories
Funding
- Department of Energy (DOE) , Office of Basic Energy Sciences, Division of Materials Sciences and Engineering [DE-SC0014430]
- U.S. Department of Energy [DE-FG02-05ER46237]
- National Energy Research Scientific Computing Center (NERSC)
- National Science Foundation through the UC Irvine Materials Research Science and Engineering Center [DMR-2011967]
- Research Grant Council of Hong Kong [24201020, 14207421]
- DOE-BES [DE-SC0018426]
- Moore Investigator in Quantum Materials [EPIQS GBMF9455]
- U.S. Department of Energy (DOE) [DE-SC0018426] Funding Source: U.S. Department of Energy (DOE)
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This study reports the discovery of curvature-induced phonon polaritons localized at the crease of folded hexagonal boron nitrides (h-BNs) using monochromated electron energy-loss spectroscopy. The creased-localized signals undergo an abnormal blue-shift, which is found to arise from the optical phonon hardening in the curled region. The study also shows that the curvature-induced phonon polariton can be controllably achieved via an electron-beam etching approach.
Generation and manipulation of phonon polaritons are of paramount importance for understanding the interaction between an electromagnetic field and dielectric materials and furthering their application in mid-infrared optical communication. However, the formation of tunable one-dimensional phonon polaritons has been rarely realized in van der Waals layered structures. Here we report the discovery of curvature-induced phonon polaritons localized at the crease of folded hexagonal boron nitrides (h-BNs) with a few atomic layers using monochromated electron energy-loss spectroscopy. Compared to bulk regions, the creased-localized signals undergo an abnormal blue-shift of 1.4 meV. First-principles calculations reveal that the energy shift arises from the optical phonon hardening in the curled region. Interestingly, the curvature-induced phonon polariton can also be controllably achieved via an electron-beam etching approach. This work opens an avenue of tailoring local electromagnetic response and creating unique phonon polariton modes in van der Waals layered materials for diverse applications.
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