Isotopic effects on in-plane hyperbolic phonon polaritons in MoO3

Published

March 4, 2024

Author(s)

Jeremy Schultz, Sergiy Krylyuk, Jeffrey Schwartz, Albert Davydov, Andrea Centrone

Abstract

Hyperbolic phonon polaritons (HPhPs), hybrids of light and lattice vibrations in polar dielectric crystals, empower nano-photonic applications by enabling the confinement and manipulation of light at the nanoscale. Molybdenum trioxide (α-MoO3) is a naturally hyperbolic material, meaning that its dielectric function deterministically controls the directional propagation of in-plane HPhPs within its reststrahlen bands. Strategies such as substrate engineering, nano- and hetero-structuring, and isotopic enrichment are being developed to alter the, otherwise, intrinsic dielectric functions of natural hyperbolic materials and control the confinement and propagation of HPhPs. Since isotopic disorder can limit phonon-based processes such as HPhPs , here we synthesize isotopically enriched 92MoO3 (92Mo: 99.93 %) and 100MoO3 (100Mo: 99.01 %) crystals to tune the properties and dispersion of HPhPs with respect to natural α MoO3, which is constituted by seven Mo stable isotopes. Real-space, near-field maps measured with the photothermal induced resonance (PTIR) technique enable comparisons of in plane HPhPs in α MoO3 and isotopically enriched analogues within a reststrahlen band (≈ 820 cm^-1 to ≈ 972 cm^-1). Results show that isotopic enrichment (e.g., 92MoO3 and 100MoO3) shifts the HPhP dispersion (angular wavenumber vs IR wavelength) by ≈ 12 % and ≈ +22 %, respectively, and changes the HPhP group velocities by ≈ ±20 %, while preserving their lifetimes (≈ 3.5 ps). Altogether, isotopic enrichment was found to offer fine control over the properties that determine the anisotropic in-plane propagation of HPhPs in α MoO3, which is essential to its implementation in nanophotonic applications.

Citation

Nanophotonics

Volume

13

Issue

9

Pub Type

Journals

Download Paper

https://doi.org/10.1515/nanoph-2023-0717

Local Download

Keywords

2D materials, hyperbolic materials, isotopic engineering, phonon polaritons, photothermal induced resonance

Citation

Schultz, J. , Krylyuk, S. , Schwartz, J. , Davydov, A. and Centrone, A. (2024), Isotopic effects on in-plane hyperbolic phonon polaritons in MoO3, Nanophotonics, [online], https://doi.org/10.1515/nanoph-2023-0717, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=956692 (Accessed December 3, 2024)