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(179) Production(s) de l'année 2023
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Confinement-Induced Nonlocality and Casimir Force in Transdimensional Systems
Auteur(s): Bondarev Igor V, Pugh Michael D, Rodriguez-Lopez Pablo, Woods Lilia M, Antezza M.
(Article) Publié:
-Phys.chem.chem.phys., vol. 25 p.29257-29265 (2023)
Texte intégral en Openaccess :
Ref HAL: hal-04174566_v1
Ref Arxiv: 2307.06452
Ref INSPIRE: 2676657
DOI: 10.1039/D3CP03706A
Ref. & Cit.: NASA ADS
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Résumé: We study within the framework of the Lifshitz theory the long-range Casimir force for in-plane isotropic and anisotropic free-standing transdimensional material slabs. In the former case, we show that the confinement-induced nonlocality not only weakens the attraction of ultrathin slabs but also changes the distance dependence of the material-dependent correction to the Casimir force to go as $\sim\!1/\!\sqrt{l}$ contrary to the $\sim\!1/l$ dependence of that of the local Lifshitz force. In the latter case, we use closely packed array of parallel aligned single-wall carbon nanotubes in a dielectric layer of finite thickness to demonstrate strong orientational anisotropy and crossover behavior for the inter-slab attractive force in addition to its reduction with decreasing slab thickness. We give physical insight as to why such a pair of ultrathin slabs prefers to stick together in the perpendicularly oriented manner, rather than in the parallel relative orientation as one would customarily expect.
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On the Brahmagupta-Fermat-Pell Equation: The Chakravāla or Cyclic algorithm revisited
Auteur(s): Mitter P.
(Document sans référence bibliographique) 2023-07-29
Ref HAL: hal-04173618_v1
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Résumé: In the following pages we take a fresh look at the ancient Indian Chakravāla or Cyclic algorithm for solving the Brahmagupta-Fermat-Pell quadratic Diophantine equation in integers taking account of recent developments. This is the oldest general algorithm (1150 CE) for solving this equation. The algorithm can be proved directly in its own terms, following a recent work by A. Bauval, to always lead to a periodic solution in a finite number of steps. We review a slightly modified version of this work. It forms the basis of a reinterpretation of this algorithm in the framework of a reduction theory of binary indefinite integer valued quadratic forms on which the modular group SL(2, Z) acts. The reduction condition of this algorithm are restated in terms of the roots of the quadratic form. The SL(2, Z) action on (reduced) roots of this form furnish semi-regular continued fractions which are periodic and which furnish SL(2, Z) automorphisms of the quadratic form. Very much as in the classical theory of Gauss, this gives solutions of the Brahmagupta-Fermat-Pell equation. We give a proof that the solution at the end of the first cycle is fundamental (positive and least). We also give the conversion to regular continued fractions which involve larger periods. A number of worked out examples are given to illustrate the main points and this for the benefit of the uninitiated reader.
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Modeling the Excitation of Graphene Magneto-plasmons in Periodic Grating of Magnetostatic Biased Graphene Ribbons
Auteur(s): Benrhouma Maha, Edee Kofi, Guizal B.
Conference: PhotonIcs & Electromagnetics Research Symposium (PIERS) (prague, CZ, 2023-07-03)
Ref HAL: hal-04172452_v1
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Résumé: We present an accurate and simple semi analytical model for studying the magneto- plasmonic response of a 1D subwavelength graphene strip grating under an external static mag- netic field. In this model, the graphene sheet is considered as an anisotropic layer with atomic thickness. Under these conditions and in contrast to the previous works, an effective medium approach (EMA) is applied to the graphene permittivity tensor and a rigorous phase correction is required to take into account the periodicity effect. The resonance phenomena occurring into the structure are taken into account in the model using the scattering matrix approach. The re- flection and transmission spectra of the structure are then given as the sum of two contributions, the scattering contribution and the single strip contribution. In order to numerically validate and evaluate the proposed model, the results have been compared with those obtained from the PMM [1, 2] method and from methods published in the literature [3, 4]. This simple approach is useful to better understand graphene surface magnetoplasmons GSMPs and may facilitate the design of various tunable devices based on graphene magnetoplasmonics.
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Enhanced and Tunable Kerr effect on InSb/graphene hybrid magnetoplasmonic structure at Terahertz waves
Auteur(s): Ben Rhouma Maha, Edee Kofi, Guizal B.
Conférence invité: META 2023 (Paris, FR, 2023-07-18)
Ref HAL: hal-04172425_v1
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Résumé: In this work, we propose a novel hybrid magneto plasmonic structure based on graphene and doped InSbto enhance the magneto optical Kerr effect at terahertz frequencies.The structure is composed of a 1D periodic dopedInSb inlayed between a metallic backgate and a dielectric/doped graphene sheet .By computing the optical responseof this structure, w e show an enhanced and large Kerr rotation in a wide range of THz frequencies compared to thatinduced by a single graphene sheet and/or a doped magnetized InSb
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Effect of top metallic contacts on radiation transfer and conversion efficiency for near-field ther- mophotovoltaics
Auteur(s): Austry K., Jeyar Y., Luo M., Guizal B., Messina R., Vaillon Rodolphe, Antezza M.
Conférence invité: META 2023 (Paris, FR, 2023-07-18)
Ref HAL: hal-04172392_v1
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Résumé: Design of the metallic contact grid at the front side of thermophotovoltaic cells is critical. Our study, based on a rigorous approach, investigates the real influence of the front metal contact grid. By modelling this grid by a metallic grating, we show that it can significantly affect the electrical power generated by the cell. Quantitative and qualitative analyses indicate behaviors which are quite different from those predicted by previous simplistic approaches.
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Efficient computation of EM scattering from a dielectric cylinder partially covered with a graphene strip
Auteur(s): Jeyar Y., Guizal B., Antezza M.
Conférence invité: META 2023 (Paris, FR, 2023-07-18)
Ref HAL: hal-04172370_v1
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Résumé: We present a numerical approach for the solution of EM scattering from a dielectric cylinder partially covered with graphene. It is based on a classical Fourier-Bessel expansion of the fields inside and outside the cylinder to which we apply the ad-hoc boundary conditions in the presence of graphene. Due to the singular nature of the electric field at the ends of the graphene sheet, we introduce auxiliary boundary conditions to better take this reality into account.
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The Fourier Modal Method simplified for crossed subwavelength gratings B. Guizal
Auteur(s): Guizal B.
Conférence invité: META 2023 (Paris, FR, 2023-07-18)
Ref HAL: hal-04171737_v1
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Résumé: We present a simplification of the Fourier Modal Method (FMM) for crossed gratings with subwavelength heights. We show that in this case it is possible to compute the scattering matrix of the structure without solving the eigenvalue problem which is the most expensive computational part of the FMM algorithm. This approach is very efficient and thus suitable for periodic metasurfaces.
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