Polariton panorama

Basov, D. N.; Asenjo-Garcı́a, Ana; Schuck, P. James; Zhu, Xiaoyang; Rubio, Ángel

doi:10.1515/nanoph-2020-0449

Cited by 232 publications

(161 citation statements)

References 513 publications

(543 reference statements)

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“…THz-SNOMs are being successfully applied to an expanding list of materials and interesting problems. For example, THz-SNOM methods have provided insights into nanoscale studies of electronic phase separation in the vicinity of the insulator-to-metal transition in VO 2 23 , 28 29 , the plasmonic response of graphene 26 – 31 , free carrier distributions in nanodevices 32 , 33 , and phonon resonances in multiferroic materials 34 .…”

Section: Introductionmentioning

confidence: 99%

Terahertz response of monolayer and few-layer WTe2 at the nanoscale

et al. 2021

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Tungsten ditelluride (WTe2) is an atomically layered transition metal dichalcogenide whose physical properties change systematically from monolayer to bilayer and few-layer versions. In this report, we use apertureless scattering-type near-field optical microscopy operating at Terahertz (THz) frequencies and cryogenic temperatures to study the distinct THz range electromagnetic responses of mono-, bi- and trilayer WTe2 in the same multi-terraced micro-crystal. THz nano-images of monolayer terraces uncovered weakly insulating behavior that is consistent with transport measurements. The near-field signal on bilayer regions shows moderate metallicity with negligible temperature dependence. Subdiffractional THz imaging data together with theoretical calculations involving thermally activated carriers favor the semimetal scenario with $$\Delta \approx -10\,{{{\rm{meV}}}}$$ Δ ≈ − 10 meV over the semiconductor scenario for bilayer WTe2. Also, we observed clear metallic behavior of the near-field signal on trilayer regions. Our data are consistent with the existence of surface plasmon polaritons in the THz range confined to trilayer terraces in our specimens. Finally, data for microcrystals up to 12 layers thick reveal how the response of a few-layer WTe2 asymptotically approaches the bulk limit.

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Section: Introductionmentioning

confidence: 99%

Terahertz response of monolayer and few-layer WTe2 at the nanoscale

et al. 2021

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“…Over the past decade, research on propagating optical polaritons in 2D materials progressed from a promising concept (1, 2) to a platform for demonstrating rich physical phenomena (3)(4)(5)(6)(7), now showing an impact on emerging opto-electronics (8,9) and nanophotonic technologies (10). These polaritons exhibit relatively low loss and long propagation distances, simultaneous with extreme confinement factors (5,(11)(12)(13)(14), facilitating their unique light-matter interactions (2,3,(15)(16)(17)(18)(19).…”

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confidence: 99%

Spatiotemporal imaging of 2D polariton wave packet dynamics using free electrons

Kurman

Dahan

Sheinfux

et al. 2021

Science

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Coherent optical excitations in two-dimensional (2D) materials, 2D polaritons, can generate a plethora of optical phenomena that arise from the extraordinary dispersion relations that do not exist in regular materials. Probing of the dynamical phenomena of 2D polaritons requires simultaneous spatial and temporal imaging capabilities and could reveal unknown coherent optical phenomena in 2D materials. Here, we present a spatiotemporal measurement of 2D wave packet dynamics, from its formation to its decay, using an ultrafast transmission electron microscope driven by femtosecond midinfrared pulses. The ability to coherently excite phonon-polariton wave packets and probe their evolution in a nondestructive manner reveals intriguing dispersion-dependent dynamics that includes splitting of multibranch wave packets and, unexpectedly, wave packet deceleration and acceleration. Having access to the full spatiotemporal dynamics of 2D wave packets can be used to illuminate puzzles in topological polaritons and discover exotic nonlinear optical phenomena in 2D materials.

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“…Over two frequency bands in the mid-infrared, referred to as the lower and upper Reststrahlen bands, the permittivity of hBN along its in-plane and out-of-plane principal axes have opposite signs 25 . Such behavior, known as hyperbolicity, leads to highly confined phonon polaritons 25 – 29 and hyperlensing effects 30 , 31 . Here, we specifically focus on the upper Reststrahlen band (1376 to 1614 cm −1 ), where hBN transverse dielectric constant in the xy -plane becomes negative ( ).…”

Section: Resultsmentioning

confidence: 99%

Hyperbolic enhancement of photocurrent patterns in minimally twisted bilayer graphene

et al. 2021

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Quasi-periodic moiré patterns and their effect on electronic properties of twisted bilayer graphene have been intensely studied. At small twist angle θ, due to atomic reconstruction, the moiré superlattice morphs into a network of narrow domain walls separating micron-scale AB and BA stacking regions. We use scanning probe photocurrent imaging to resolve nanoscale variations of the Seebeck coefficient occurring at these domain walls. The observed features become enhanced in a range of mid-infrared frequencies where the hexagonal boron nitride substrate is optically hyperbolic. Our results illustrate the capabilities of the nano-photocurrent technique for probing nanoscale electronic inhomogeneities in two-dimensional materials.

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Polariton panorama

Cited by 232 publications

References 513 publications

Terahertz response of monolayer and few-layer WTe2 at the nanoscale

Terahertz response of monolayer and few-layer WTe2 at the nanoscale

Spatiotemporal imaging of 2D polariton wave packet dynamics using free electrons

Hyperbolic enhancement of photocurrent patterns in minimally twisted bilayer graphene

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