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(295) Production(s) de l'année 2019
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High-Pressure Softening of the Out-of-Plane A2u(Transverse-Optic) Mode of Hexagonal Boron Nitride Induced by Dynamical Buckling
Auteur(s): Segura A, Cusco R., Taniguchi T., Watanabe Kanji, Cassabois G., Gil B., Artus L.
(Article) Publié:
The Journal Of Physical Chemistry C, vol. 123 p.17491 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02192575_v1
DOI: 10.1021/acs.jpcc.9b04582
WoS: 000476693800050
Exporter : BibTex | endNote
6 Citations
Résumé: We investigate the highly anisotropic behavior of the in-plane and out-of-plane infrared-active phonons of hexagonal boron nitride by means of infrared reflectivity and absorption measurements under high pressure. Infrared reflectivity spectra at normal incidence on high-quality single crystals show strict fulfillment of selection rules and an unusually long E1u[transverse-optic (TO)] phonon lifetime. Accurate values of the dielectric constants at ambient pressure ε⊥0 = 6.96, ε⊥∞ = 4.95, ε∥0 = 3.37, and ε∥∞ = 2.84 have been determined from fits to the reflectivity spectra. The out-of-plane A2u phonon reflectivity band is revealed in measurements on an inclined facet, and absorption measurements at an incidence angle of 30° allow us to observe both the transverse- and longitudinal-optic A2u modes. Pressure coefficients and Grüneisen parameters for all infrared-active modes are determined and compared with ab initio calculations. While Grüneisen parameters are generally small in this layered crystal, the A2u(TO) displays an exceptionally large and negative Grüneisen parameter that results in widening of the type I hyperbolic region with increasing pressure. Softening of the A2u(TO) mode is induced by dynamical buckling of the flat honeycomb layers.
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Spatiotemporal Spin Noise Spectroscopy
Auteur(s): Cronenberger S., Abbas C., Scalbert D., Boukari H.
(Article) Publié:
Physical Review Letters, vol. 123 p.017401 (2019)
Ref HAL: hal-02192421_v1
DOI: 10.1103/PhysRevLett.123.017401
WoS: WOS:000473540500009
Exporter : BibTex | endNote
3 Citations
Résumé: We report on the potential of a new spin noise spectroscopy approach by demonstrating all-optical probing of spatiotemporal spin fluctuations. This is achieved by homodyne mixing of a spatially phase-modulated local oscillator with spin-flip scattered light, from which the frequency and wave vector dependence of the spin noise power is unveiled. As a first application of the method we measure the spatiotemporal spin noise in weakly n-doped CdTe layers, from which the electron spin diffusion constant and spin relaxation rates are determined. The absence of spatial spin correlations is also shown for this particular system.
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Photonics with hexagonal boron nitride
Auteur(s): Caldwell Joshua David, Aharonovich Igor, Cassabois G., Edgar James H., Gil B., Basov D.N.
(Article) Publié:
Nature Reviews Materials, vol. 8 p.1 (2019)
Ref HAL: hal-02191041_v1
DOI: 10.1038/s41578-019-0124-1
WoS: 000478802800006
Exporter : BibTex | endNote
71 Citations
Résumé: For more than seven decades, hexagonal boron nitride (hBN) has been employed asan inert, thermally stable engineering ceramic; since 2010, it has also been used as the optimal substrate for graphene in nanoelectronic and optoelectronic devices. Recent research has revealed that hBN exhibits a unique combination of optical properties that enable novel (nano) photonic functionalities. Specifically, hBN is a natural hyperbolic material in the mid-IR range,in which photonic material options are sparse. Furthermore, hBN hosts defects that can be engineered to obtain room-temperature, single-photon emission; exhibits strong second-order nonlinearities with broad implications for practical devices; and is a wide-bandgap semiconductor well suited for deep UV emitters and detectors. Inspired by these promising attributes, research on the properties of hBN and the development of large-area bulk and thin-film growth techniques has dramatically expanded. This Review offers a snapshot of current research exploring the properties underlying the use of hBN for future photonics functionalities and potential applications, and covers some of the remaining obstacles.
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Giant interatomic energy-transport amplification with nonreciprocal photonic topological insulators
Auteur(s): Doyeux P., Hassani gangaraj S. ali, Hanson George w., Antezza M.
Conférence invité: Frontiers of Quantum and Mesoscopic Thermodynamics - FQMT19 (Prague, CZ, 2019-07-15)
Ref HAL: hal-02190897_v1
Exporter : BibTex | endNote
Résumé: We show that the energy-transport efficiency in a chain of two-level emitters can be drastically enhancedby the presence of a photonic topological insulator (PTI). This is obtained by exploiting the peculiarproperties of its nonreciprocal surface plasmon polariton (SPP), which is unidirectional, and immune tobackscattering, and propagates in the bulk band gap. This amplification of transport efficiency can be asmuch as 2 orders of magnitude with respect to reciprocal SPPs. Moreover, we demonstrate that despite thepresence of considerable imperfections at the interface of the PTI, the efficiency of the SPP-assisted energytransport is almost unaffected by discontinuities. We also show that the SPP properties allow energytransport over considerably much larger distances than in the reciprocal case, and we point out aparticularly simple way to tune the transport. Finally, we analyze the specific case of a two-emitter chainand unveil the origin of the efficiency amplification. The efficiency amplification and the practicaladvantages highlighted in this work might be particularly useful in the development of new devicesintended to manage energy at the atomic scale.
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Giant Interatomic Energy-transport Amplification with Nonreciprocal Photonic Topological Insulators
Auteur(s): Doyeux P., Hassani gangaraj S. ali, Hanson George w., Antezza M.
Conférence invité: PIERS 2019 (Rome, IT, 2019-06-20)
Ref HAL: hal-02190893_v1
Exporter : BibTex | endNote
Résumé: We show that the energy-transport efficiency in a chain of two-level emitters can be drastically enhancedby the presence of a photonic topological insulator (PTI). This is obtained by exploiting the peculiarproperties of its nonreciprocal surface plasmon polariton (SPP), which is unidirectional, and immune tobackscattering, and propagates in the bulk band gap. This amplification of transport efficiency can be asmuch as 2 orders of magnitude with respect to reciprocal SPPs. Moreover, we demonstrate that despite thepresence of considerable imperfections at the interface of the PTI, the efficiency of the SPP-assisted energytransport is almost unaffected by discontinuities. We also show that the SPP properties allow energytransport over considerably much larger distances than in the reciprocal case, and we point out aparticularly simple way to tune the transport. Finally, we analyze the specific case of a two-emitter chainand unveil the origin of the efficiency amplification. The efficiency amplification and the practicaladvantages highlighted in this work might be particularly useful in the development of new devicesintended to manage energy at the atomic scale.
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Long-range Heat and Energy Transfer through Hyperbolic Materials
Auteur(s): Biehs Svend-Age, Messina R., Guizal B., Antezza M., Ben-Abdallah Philippe, Deshmukh R., Galfsky T., Menon V, Agarwal G. S.
Conférence invité: PIERS 2019 (Rome, IT, 2019-06-20)
Ref HAL: hal-02190887_v1
Exporter : BibTex | endNote
Résumé: Heat flux exchanged between two hot bodies at subwavelength separation distances can exceed the limitpredicted by the blackbody theory. However, this super-Planckian transfer is restricted to these separationdistances. Here we demonstrate the possible existence of a super-Planckian transfer at arbitrary large separationdistances if the interacting bodies are connected in the near field with weakly dissipating hyperbolic waveguides.This result opens the way to long-distance transport of near-field thermal energy.
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4D compressive sensing holographic microscopy imaging of small moving objects
Auteur(s): Brodoline A., Rawat Nitin, Alexandre D., Cubedo Nicolas, Gross M.
(Article) Publié:
Optics Letters, vol. 44 p.2827 (2019)
Texte intégral en Openaccess :
Ref HAL: hal-02189448_v1
DOI: 10.1364/OL.44.002827
WoS: 000469838100055
Exporter : BibTex | endNote
11 Citations
Résumé: We show that compressive sensing (CS) calculations are very ecient to reconstruct in 3D sparse objects whose 2D hologram has been recorded by digital holographic microscopy. The method is well adapted to image small scattering objects moving within a larger motionless object. This situation corresponds to red blood cells (RBCs) circulating in the vascular system of a zebrash (Danio rerio) larva. RBCs positions are imaged in 3D from a single hologram, while the RBCs trajectories, i.e. the perfused blood vessels, are imaged from a sequence of holograms. With respect to previous work (Donnarumma et al., Opt. express, 24, 26887, 2016), we get a gain of ∼ 500 in calculation speed.
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