Long-Lived Phonon Polaritons in Hyperbolic Materials

Natural hyperbolic materials with dielectric permittivities of opposite signs along different principal axes can confine long-wavelength electromagnetic waves down to the nanoscale, well below the diffraction limit. Confined electromagnetic waves coupled to phonons in hyperbolic dielectrics includin...

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Bibliographic Details
Authors: Ni, Guangxin, McLeod, Alexander S., Sun, Zhiyuan, Matson, Joseph R., Lo, Chiu Fan Bowen, Rhodes, Daniel A., Ruta, Francesco L., Moore, Samuel L., Vitalone, Rocco A., Cuscó, Ramón, Artús, Lluís, Xiong, Lin, Dean, Cory R., Hone, James C., Millis, Andrew J., Fogler, Michael M., Edgar, James H., Caldwell, Joshua D., Basov, D. N.
Format: article
Status:Versión enviada para evaluación y publicación
Publication Date:2021
Country:España
Institution:Consejo Superior de Investigaciones Científicas (CSIC)
Repository:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/244312
Online Access:http://hdl.handle.net/10261/244312
Access Level:Open access
Keyword:Phonon polaritons
Van der Waals heterostructures
Hyperbolic materials
Nanoinfrared imaging
Description
Summary:Natural hyperbolic materials with dielectric permittivities of opposite signs along different principal axes can confine long-wavelength electromagnetic waves down to the nanoscale, well below the diffraction limit. Confined electromagnetic waves coupled to phonons in hyperbolic dielectrics including hexagonal boron nitride (hBN) and α-MoO3 are referred to as hyperbolic phonon polaritons (HPPs). HPP dissipation at ambient conditions is substantial, and its fundamental limits remain unexplored. Here, we exploit cryogenic nanoinfrared imaging to investigate propagating HPPs in isotopically pure hBN and naturally abundant α-MoO3 crystals. Close to liquid-nitrogen temperatures, losses for HPPs in isotopic hBN drop significantly, resulting in propagation lengths in excess of 8 μm, with lifetimes exceeding 5 ps, thereby surpassing prior reports on such highly confined polaritonic modes. Our nanoscale, temperature-dependent imaging reveals the relevance of acoustic phonons in HPP damping and will be instrumental in mitigating such losses for miniaturized mid-infrared technologies operating at liquid-nitrogen temperatures.

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