Few-layer hexagonal boron nitride as a shield of brittle materials for cryogenic s-SNOM exploration of phonon polaritons

Hu, Debo; Luo, Cheng; Kang, Lixing; Liu, Mengkun; Dai, Qing

doi:10.1063/5.0081203

Cited by 6 publications

(2 citation statements)

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“…At cryogenic temperatures, CrSBr contaminated s-SNOM tips during scanning. To overcome this, we encapsulated CrSBr with a thin ( ) hexagonal boron nitride (hBN) layer 53 . Exfoliated hBN is picked up using the standard dry-transfer technique.…”

Section: Methodsmentioning

confidence: 99%

Hyperbolic exciton polaritons in a van der Waals magnet

Ruta,

Zhang,

Shao

et al. 2023

Nat Commun

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Exciton polaritons are quasiparticles of photons coupled strongly to bound electron-hole pairs, manifesting as an anti-crossing light dispersion near an exciton resonance. Highly anisotropic semiconductors with opposite-signed permittivities along different crystal axes are predicted to host exotic modes inside the anti-crossing called hyperbolic exciton polaritons (HEPs), which confine light subdiffractionally with enhanced density of states. Here, we show observational evidence of steady-state HEPs in the van der Waals magnet chromium sulfide bromide (CrSBr) using a cryogenic near-infrared near-field microscope. At low temperatures, in the magnetically-ordered state, anisotropic exciton resonances sharpen, driving the permittivity negative along one crystal axis and enabling HEP propagation. We characterize HEP momentum and losses in CrSBr, also demonstrating coupling to excitonic sidebands and enhancement by magnetic order: which boosts exciton spectral weight via wavefunction delocalization. Our findings open new pathways to nanoscale manipulation of excitons and light, including routes to magnetic, nonlocal, and quantum polaritonics.

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Section: Methodsmentioning

confidence: 99%

Hyperbolic exciton polaritons in a van der Waals magnet

Ruta,

Zhang,

Shao

et al. 2023

Nat Commun

View full text Add to dashboard Cite

show abstract

“…At cryogenic temperatures, CrSBr contaminated s-SNOM tips during scanning. To overcome this, we encapsulated CrSBr with a thin (<10nm) hexagonal boron nitride (hBN) layer 53 . Exfoliated hBN is picked up using the standard dry-transfer technique.…”

Section: Stacking and Transfermentioning

confidence: 99%

Hyperbolic exciton polaritons in a van der Waals magnet

Ruta,

Zhang,

Shao

et al. 2023

Preprint

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Exciton polaritons are quasiparticles of photons coupled strongly to bound electron-hole pairs, manifesting as an anti-crossing light dispersion near an exciton resonance. Highly-anisotropic semiconductors with opposite-signed permittivities along different crystal axes are predicted to host exotic modes called hyperbolic exciton polaritons (HEPs), which permit spatial confinement beyond the material light cone and enhanced density of states. Here, we show the first observational evidence of steady-state HEPs using a cryogenic near-field microscope in the van der Waals magnet chromium sulfide bromide. At low temperature, in the magnetically-ordered state, anisotropic exciton resonances sharpen, driving the permittivity negative along one crystal axis and enabling HEP propagation. Further, we demonstrate coupling of HEPs to excitonic sidebands and increasing exciton spectral weight near the magnetic transitions corresponding to exciton wavefunction delocalization. Our findings open new pathways to nanoscale manipulation of excitons and light, including routes to magnetic, nonlocal, and quantum polaritonics in a light-emitting material.

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