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(222) Production(s) de l'année 2022
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Atomic-Spring-like Effect in Glassy Silica-Helium Composites br
Auteur(s): Bowron Daniel T., Keen David A., Kint M., Weigel C., Ruffle B., Konczewicz L., Contreras S., Coasne Benoit, Garbarino Gaston, Beaudhuin Mickael, Haines Julien, Rouquette Jerome
(Article) Publié:
The Journal Of Physical Chemistry C, vol. 126 p.5722-5727 (2022)
Ref HAL: hal-03669554_v1
DOI: 10.1021/acs.jpcc.2c00026
WoS: WOS:000783122600037
Exporter : BibTex | endNote
Résumé: We determine the structural origin of an “atomic-spring-like effect”in a glassy silica-helium composite, which exhibits this mechanical property thatreversibly accumulates and restores energy at the subnanoscale based on a high-pressure experimental pair distribution function study combined with atom-scalemolecular simulations. These unexpected experimental results were obtained byusing a 3 μm spot size 61 keV X-ray beam and large area detector and bysubtracting the scattered intensity due to helium outside the sample from the silicasignal at the same focal point for each pressure point. The compression behavior ofthe glassy silica-helium composite is characterized on a structural level by the change from a uni- to bimodal distribution in the inter- tetrahedral distances in the amorphous isotropic structure of silica. We propose a simple characterization of this atomic-spring-like glass property using impedance spectroscopy measurements.
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Detection of Single W-Centers in Silicon
Auteur(s):
(Article) Publié:
Acs Photonics, vol. 9 p.2337-2345 (2022)
Texte intégral en Openaccess :
Ref HAL: hal-03667803_v1
Ref Arxiv: 2108.04283
Ref INSPIRE: 2074104
DOI: 10.1021/acsphotonics.2c00336
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: Controlling the quantum properties of individual fluorescent defects in silicon is a key challenge toward large-scale advanced quantum photonic devices. Research efforts have so far focused on extrinsic defects based on impurities incorporated inside the silicon lattice. Here, we demonstrate the detection of single intrinsic defects in silicon, which are linked to a tri-interstitial complex called the W-center, with a zero-phonon line at 1.218 μm. Investigating their single-photon emission properties reveals new information about this common radiation damage center, such as its dipolar orientation and its photophysics. We also identify its microscopic structure and show that, although this defect does not feature electronic states in the bandgap, Coulomb interactions lead to excitonic radiative recombination below the silicon bandgap. These results could set the stage for numerous quantum perspectives based on intrinsic luminescent defects in silicon, such as integrated quantum photonics and quantum communications.
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Single G centers in silicon fabricated by co-implantation with carbon and proton
Auteur(s):
(Article) Publié:
-Appl.phys.lett., vol. 121 p.084003 (2022)
Texte intégral en Openaccess :
Ref HAL: hal-03667801_v1
Ref Arxiv: 2204.13521
Ref INSPIRE: 2074228
DOI: 10.1063/5.0097407
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: We report the fabrication of G centers in silicon with an areal density compatible with single photon emission at optical telecommunication wavelengths. Our sample is made from a silicon-on-insulator wafer which is locally implanted with carbon ions and protons at various fluences. Decreasing the implantation fluences enables to gradually switch from large ensembles to isolated single defects, reaching areal densities of G centers down to $\sim$0.2 $\mu$m$^{-2}$. Single defect creation is demonstrated by photon antibunching in intensity-correlation experiments, thus establishing our approach as a reproducible procedure for generating single artificial atoms in silicon for quantum technologies.
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D-instantons and superpotential
Auteur(s): Alexandrov S.
Conférence invité: Strings and Geometry 2022 (Utrecht, NL, 2022-05-02)
Ref HAL: hal-03664125_v1
Exporter : BibTex | endNote
Résumé: I'll present the computation of a D-instanton induced superpotential in an orientifold Calabi-Yau compactification of type II string theory using a direct worldsheet approach.
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D-instantons in string compactifications
Auteur(s): Alexandrov S.
Conference: Eurostrings 2022 (Lyon, FR, 2022-04-25)
Ref HAL: hal-03664123_v1
Exporter : BibTex | endNote
Résumé: Euclidean D-branes wrapped on non-trivial cycles of a Calabi-Yau threefold are known to affect the metric on the hypermultiplet moduli space determining the effective action of type II strings on such manifolds. After reviewing the existing results on the instanton corrected metric following from a combination of constraints imposed by supersymmetry and dualities, I'll show how the D-instanton effects can be computed by a direct worldsheet approach. It required solving several conceptual and technical problems and has recently been extended to compactifications with lower supersymmetry. The talk is based on joint work with A. Sen and B. Stefanski.
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Microscopic origin of excess wings in relaxation spectra of supercooled liquids
Auteur(s): Guiselin B., Scalliet C., Berthier L.
(Article) Publié:
Nature Physics, vol. 18 p.468-+ (2022)
Texte intégral en Openaccess :
Ref HAL: hal-03662093_v1
Ref Arxiv: 2103.01569
DOI: 10.1038/s41567-022-01508-z
WoS: WOS:000770232200001
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: Glass formation is encountered in diverse materials. Experiments have revealed that dynamic relaxation spectra of supercooled liquids generically become asymmetric near the glass transition temperature, Tg, where an extended power law emerges at high frequencies. The microscopic origin of this "wing" remains unknown, and was so far inaccessible to simulations. Here, we develop a novel computational approach and study the equilibrium dynamics of model supercooled liquids near Tg. We demonstrate the emergence of a power law wing in numerical spectra, which originates from relaxation at rare, localised regions over broadly-distributed timescales. We rationalise the asymmetric shape of relaxation spectra by constructing an empirical model associating heterogeneous activated dynamics with dynamic facilitation, which are the two minimal physical ingredients revealed by our simulations. Our work offers a glimpse of the molecular motion responsible for glass formation at relevant experimental conditions.
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Imaging Topological Defects in a Noncollinear Antiferromagnet
Auteur(s): Finco A., Haykal A., Fusil Stéphane, Kumar P., Dufour Pauline, Forget Anne, Colson Dorothée, Chauleau Jean-Yves, Viret Michel, Jaouen Nicolas, Garcia V, Jacques V.
(Article) Publié:
Physical Review Letters, vol. 128 p.187201 (2022)
Texte intégral en Openaccess :
Ref HAL: hal-03659802_v1
DOI: 10.1103/PhysRevLett.128.187201
Exporter : BibTex | endNote
Résumé: We report on the formation of topological defects emerging from the cycloidal antiferromagnetic order at the surface of bulk BiFeO3 crystals. Combining reciprocal and real-space magnetic imaging techniques, we first observe, in a single ferroelectric domain, the coexistence of antiferromagnetic domains in which the antiferromagnetic cycloid propagates along different wave vectors. We then show that the direction of these wave vectors is not strictly locked to the preferred crystallographic axes as continuous rotations bridge different wave vectors. At the junctions between the magnetic domains, we observe topological line defects identical to those found in a broad variety of lamellar physical systems with rotational symmetries. Our work establishes the presence of these magnetic objects at room temperature in the multiferroic antiferromagnet BiFeO3, offering new possibilities for their use in spintronics
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