Observation of naturally canalized phonon polaritons in LiV<sub>2</sub>O<sub>5</sub> thin layers.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38538588.
- Also identified by DOI 10.1038/s41467-024-46935-z and PMC identifier 10973474.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Polariton canalization is characterized by intrinsic collimation of energy flow along a single crystalline axis. This optical phenomenon has been experimentally demonstrated at the nanoscale by stacking and twisting van der Waals (vdW) layers of α-MoO<sub>3</sub>, by combining α-MoO<sub>3</sub> and graphene, or by fabricating an h-BN metasurface. However, these material platforms have significant drawbacks, such as complex fabrication and high optical losses in the case of metasurfaces. Ideally, it would be possible to canalize polaritons "naturally" in a single pristine layer. Here, we theoretically predict and experimentally demonstrate naturally canalized phonon polaritons (PhPs) in a single thin layer of the vdW crystal LiV<sub>2</sub>O<sub>5</sub>. In addition to canalization, PhPs in LiV<sub>2</sub>O<sub>5</sub> exhibit strong field confinement ( <math xmlns="http://www.w3.org/1998/Math/MathML"> <msub><mrow><mi>λ</mi></mrow> <mrow><mi>p</mi></mrow> </msub> <mo>~</mo> <mfrac> <mrow> <msub><mrow><mi>λ</mi></mrow> <mrow><mi>0</mi></mrow> </msub> </mrow> <mrow><mi>27</mi></mrow> </mfrac> </math> ), slow group velocity (0.0015c), and ultra-low losses (lifetimes of 2 ps). Our findings are promising for the implementation of low-loss optical nanodevices where strongly directional light propagation is needed, such as waveguides or optical routers.