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Théorie du rayonnement matière et phénomènes quantiques
(9) Production(s) de l'année 2021
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Dynamical polarizability of graphene with spatial dispersion 
Auteur(s): Zhu Tao, Antezza M., Wang Jian-Sheng
(Article) Publié:
Physical Review B, vol. 103 p.125421 (2021)
Texte intégral en Openaccess : 
Ref HAL: hal-03176682_v1
DOI: 10.1103/PhysRevB.103.125421
Exporter : BibTex | endNote
Résumé: We perform a detailed analysis of electronic polarizability of graphene with different theoretical approaches.From Kubo’s linear response formalism, we give a general expression of frequency and wave-vector dependentpolarizability within the random phase approximation. Four theoretical approaches have been applied to thesingle-layer graphene and their differences are on the band overlap of wave functions. By comparing with theab initio calculation, we discuss the validity of methods used in literature. Our results show that the tightbinding method is as good as the time-demanding ab initio approach in calculating the polarizability of graphene.Moreover, due to the special Dirac-cone band structure of graphene, the Dirac model reproduces results of thetight-binding method for energy smaller than 3 eV. For doped graphene, the intraband transitions dominateat low energies and can be described by the Lindhard formula for two-dimensional electron gases. At zerotemperature and long-wavelength limit, with the relaxation time approximation, all theoretical methods reduceto a long-wave analytical formula and the intraband contributions agree to the Drude polarizability of graphene.Effects of electrical doping and temperature are also discussed. This work may provide a solid reference forresearches and applications of the screening effect of graphene.
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Strong geometry dependence of the Casimir force between interpenetrated rectangular gratings
Auteur(s): Wang Mingkang, Tang Lu, Messina C. Y. Ng Riccardo, Guizal B., Crosse J. A., Antezza M., Chan Che Ting, Chan Ho Bun
(Article) Publié:
Nature Communications, vol. 12 p.600 (2021)
Texte intégral en Openaccess : 
Ref HAL: hal-03122200_v1
DOI: 10.1038/s41467-021-20891-4
Exporter : BibTex | endNote
Résumé: Quantum fluctuations give rise to Casimir forces between two parallel conducting plates, the magnitude of which increases monotonically as the separation decreases. By introducing nanoscale gratings to the surfaces, recent advances have opened opportunities for controlling the Casimir force in complex geometries. Here, we measure the Casimir force between two rectangular silicon gratings. Using an on-chip detection platform, we achieve accurate alignment between the two gratings so that they interpenetrate as the separation is reduced. Just before interpenetration occurs, the measured Casimir force is found to have a geometry dependence that is much stronger than previous experiments, with deviations from the proximity force approximation reaching a factor of ~500. After the gratings interpenetrate each other, the Casimir force becomes non-zero and independent of displacement. This work shows that the presence of gratings can strongly modify the Casimir force to control the interaction between nanomechanical components.
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