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(157) Production(s) de l'année 2018


Coherent population trapping with a controlled dissipation: applications in optical metrology
Auteur(s): Nicolas L., Delord T, Jamonneau P, Coto R, Maze J, Jacques V., Hétet G
(Article) Publié:
New Journal Of Physics, vol. 20 p.033007 (2018)
Texte intégral en Openaccess :
Ref HAL: hal01768796_v1
DOI: 10.1088/13672630/aab574
Exporter : BibTex  endNote
Résumé: We analyze the properties of a pulsed coherent population trapping protocol that uses a controlled decay from the excited state in a Λlevel scheme. We study this problem analytically and numerically and find regimes where narrow transmission, absorption, or fluorescence spectral lines occur. We then look for optimal frequency measurements using these spectral features by computing the Allan deviation in the presence of ground state decoherence and show that the protocol is on a par with RamseyCPT. We discuss possible implementations with ensembles of alkali atoms and single ions and demonstrate that typical pulsedCPT experiments that are realized on femtosecond timescales can be implemented on microseconds timescales using this scheme.



Nexttominimal dark matter at the LHC
Auteur(s): Bharucha Aoife, BRÜMMER Felix, Desai N.
(Document sans référence bibliographique) Texte intégral en Openaccess :
Ref HAL: hal01767365_v1
Ref Arxiv: 1804.02357
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: We examine the collider signatures of a WIMP dark matter scenario comprising a singlet fermion and an SU(2) nplet fermion, with a focus on n=3 and n=5. The singlet and nplet masses are of the order of the electroweak scale. The nplet contains new charged particles which will be copiously pairproduced at the LHC. Small mixing angles and neardegenerate masses, both of which feature naturally in these models, give rise to longlived particles and their characteristic collider signatures. In particular, the n=5 model can be constrained by displaced lepton searches independently of the mixing angle, generically ruling out 5plet masses below about 280 GeV. For small mixing angles, we show that there is a parameter range for which the model reproduces the observed thermal relic density but is severely constrained by disappearing track searches in both the n=3 and the n=5 cases. The n=3 model is further constrained by soft dilepton searches irrespectively of whether any new particles are longlived.
Commentaires: 16 pages, 5 figures



Aggregate Formation of SurfaceModified Nanoparticles in Solvents and Polymer Nanocomposites
Auteur(s): Musino D., Genix A.C., Chaussee Thomas, Guy Laurent, Meissner Natalia, Kozak Radoslaw, Bizien Thomas, Oberdisse J.
(Article) Publié:
Langmuir, vol. 34 p.30103020 (2018)
Ref HAL: hal01768107_v1
DOI: 10.1021/acs.langmuir.7b03932
Exporter : BibTex  endNote
Résumé: A new method based on the combination of smallanglescattering, reverse Monte Carlo simulations, and an aggregate recognition algorithm is proposed to characterize the structure of nanoparticle suspensions in solvents and polymer nanocomposites, allowing detailedstudies of the impact of different nanoparticle surface modifications.Experimental smallangle scattering is reproduced using simulated annealing of configurations of polydisperse particles in a simulation box compatible with the lowest experimental qvector. Then, properties of interest likeaggregation states are extracted from these configurations and averaged. This approach has been applied to silane surfacemodified silica nanoparticles with different grafting groups, in solvents and after casting into polymer matrices.It is shown that the chemistry of the silane function, in particular mono or trifunctionality possibly related to patch formation, affects the dispersion state in a given medium, in spite of an unchanged alkylchain length. Our approach may be applied to study any dispersion or aggregation state of nanoparticles. Concerningnanocomposites, the method has potential impact on the design of new formulations allowing controlled tuning of nanoparticle dispersion.



Exciton Bound to 1D Intersection of Stacking Fault Plane with a ZnSe Quantum Well
Auteur(s): Smirnov Dmitry s., Belyaev Kirill g., Kirilenko Demid a., Nestoklon Mikhail o., Rakhlin Maxim v., Toropov Alexey a., Sedova Irina v., Sorokin Sergey v., Ivanov Sergey v., Gil B., Shubina Tatiana v.
(Article) Publié:
Physica Status Solidi  Rapid Research Letters, vol. 12 p.1700410 (2018)
Ref HAL: hal01767307_v1
DOI: 10.1002/pssr.201700410
Exporter : BibTex  endNote
Résumé: Emerging part of condensed matter science, which deals with the systems of extreme twodimensionality, renews the interest in natural 2D objects such as planar stacking faults (SFs) in semiconductor crystals. We report on the observation of an excitonic state localized at the 1D intersection of the SF with a high quality ZnSe quantum well (QW). The microphotoluminescence measurements are performed in a specimen used for preceding transmission electron microscopy studies. We demonstrate that the observed narrow lines are polarized along SFs and their linewidths depend on the SFs length. For short SFs, the linewidth can be as low as 0.15 meV. Using the combination of the effective mass approach and the density functional theory calculations we show that the exciton localization is due to the intrinsic electric field inside the SF, which also leads to a spatial separation of electron and hole in the exciton. The 1D intersection of perfect natural and artificial 2D objects can serve as a promising playground for the study of subtle excitonic effects in single defects.



Local order and crystallization of dense polydisperse hard spheres
Auteur(s): Coslovich D., Ozawa M., Berthier L.
(Article) Publié:
Journal Of Physics: Condensed Matter, vol. 30 p.144004 (2018)
Texte intégral en Openaccess :
Ref HAL: hal01767275_v1
Ref Arxiv: 1801.09638
DOI: 10.1088/1361648X/aab0c9
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
Résumé: Computer simulations give precious insight into the microscopic behavior of supercooled liquids and glasses, but their typical time scales are orders of magnitude shorter than the experimentally relevant ones. We recently closed this gap for a class of models of size polydisperse fluids, which we successfully equilibrate beyond laboratory time scales by means of the swap Monte Carlo algorithm. In this contribution, we study the interplay between compositional and geometric local orders in a model of polydisperse hard spheres equilibrated with this algorithm. Local compositional order has a weak state dependence, while local geometric order associated to icosahedral arrangements grows more markedly but only at very high density. We quantify the correlation lengths and the degree of sphericity associated to icosahedral structures and compare these results to those for the Wahnström LennardJones mixture. Finally, we analyze the structure of very dense samples that partially crystallized following a pattern incompatible with conventional fractionation scenarios. The crystal structure has the symmetry of aluminum diboride and involves a subset of small and large particles with size ratio approximately equal to 0.5.



Chemical & Nanomechanical Study of Artificial Human Enamel Subsurface Lesions
Auteur(s): Alobaidi R., Salehi H., Desoutter A., Bonnet L., Etienne P., Terrer E., Jacquot B., Levallois B., Tassery H., Cuisinier F. J. G.
(Article) Publié:
Scientific Reports, vol. 8 p.4047 (2018)
Texte intégral en Openaccess :
Ref HAL: hal01767245_v1
DOI: 10.1038/s41598018224597
Exporter : BibTex  endNote
Résumé: White lesions represent an early phase of caries formation. 20 human sound premolars were subjected to pH cycling procedure to induce subsurface lesions (SLs) in vitro. In addition, 2 teeth with naturally developed white spot lesions (WSLs) were used as references. All specimens characterized by confocal Raman microscopy being used for the first time in examining white & subsurface lesions and providing a high resolution chemical and morphological map based on phosphate peak intensity alterations at 960 cm−1. Nanoindentation technique was used to measure Hardness (H) and Young’s modulus (E) of enamel. Phosphate map of examined samples exhibited presence of intact surface layer (ISL) followed by severe depletion in (PO43−) peak in the area corresponding to the body of the lesion. In all examined groups, the mechanical properties of enamel were decreased in lesion area and found to be inversely related to penetration depth of indenter owing to enamel hierarchical structure. By combining the above two techniques, we linked mechanical properties of enamel to its chemical composition and ensured that the two methods are highly sensitive to detect small changes in enamel composition. Further work is required to bring these two excellent tools to clinical application to perceive carious lesions at an early stage of development.



Homogenous static magnetic field coils dedicated to portable nuclear magnetic resonance for agronomic studies
Auteur(s): SidiBoulenouar Rahima, Reis Ariston, Nativel Eric, Buy Simon, de Pellegars Pauline, Liu Pan, Zanca M., GozeBac C., Barbat J., Alibert E., Verdeil JeanLuc, Gatineau Frederic, Bertin Nadia, Anand Atma, Coillot C.
(Article) Publié:
Journal Of Sensors And Sensor Systems, vol. 7 p.227  234 (2018)
Texte intégral en Openaccess :
