Ref HAL: hal-01223677_v1
DOI: 10.1103/PhysRevB.91.205308
WoS: WOS:000354972700009
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3 Citations
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Giant Kerr rotation and ellipticity are observed and investigated in an asymmetric planar microcavity with a quantum well in the active region. Rotation angle of the polarization plane as well as ellipticity were determined from time- and frequency-resolved measurements of the Stokes vector components of reflected light. It was found that in a small range of the cavity mode detunings the polarized pump pulse creates a large splitting of the lower polariton branch while leaving its linewidth almost the same. This fact gives a possibility to observe at such detunings the Kerr rotation angle and ellipticity, close to their extremes. A theoretical analysis shows that the decisive role in reaching extreme polarization rotation angles is played by the structure asymmetry. Comprehensive analysis of the polarization state of the light in this regime shows that both renormalization of the exciton energy and the saturation of the excitonic resonance contribute to the observed optical nonlinearities.

Ref HAL: hal-01223011_v1
DOI: 10.1088/0953-8984/27/42/425201
WoS: 000362573500003
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2 Citations

Ref HAL: hal-01221446_v1
DOI: 10.1021/acs.langmuir.5b02833
WoS: 000362920900005
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20 Citations
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An original protocol of simultaneous surface modification and transfer from aqueous to organic phases of anatase TiO2 nanoparticles (NPs) using alkylphosphonic acids (PAs) is studied. The influence of the solvent, the nature and concentration of the PA, and the size, concentration, and aggregation state of the TiO2 NPs was investigated. Complete transfer was observed for linear alkyl chains (5, 8, 12, and 18 C atoms), even at very high sol concentrations. After transfer, the grafted NPs were characterized by 31P solid-state MAS NMR. The dispersion state of NPs before and after phase transfer was monitored by dynamic light scattering (DLS). Small-angle neutron scattering (SANS) was used to characterize the structure of PA-grafted NPs in the organic solvent. Using a quantitative core?shell model cross-checked under different contrast conditions, it is found that the primary particles making up the NPs are homogeneously grafted with a solvated PA-layer. The nanometric thickness of the latter is shown to increase with the length of the linear carbon chain of the PA, independent of the size of the primary TiO2 NP. Interestingly, a reversible temperature-dependent aggregation was evidenced visually for C18PA, and confirmed by DLS and SANS: heating the sample induces the breakup of aggregates, which reassemble upon cooling. Finally, in the case of NPs agglomerated by playing with the pH or the salt concentration of the sols, the phase transfer with PA is capable of redispersing the agglomerates. This new and highly versatile method of NP surface modification with PAs and simultaneous transfer is thus well suited for obtaining well-dispersed grafted NPs.

Ref HAL: hal-01219144_v1
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In this work we report on the response of asymmetric graphene based devices to subterahertz and terahertz radiation. Our devices are made in a configuration of a field-effect transistor with conduction channel between the source and drain electrodes formed with a CVD-grown graphene. The radiation is coupled through a spiral antenna to source and top gate electrodes. Room temperature responsivity of our devices is close to the values that are attractive for commercial applications. Further optimization of the device configuration may result in appearance of novel terahertz radiation detectors.

Ref HAL: hal-01218489_v1
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Casein micelles (CMs) are colloidal protein-mineral complexes in equilibrium in the milk serum. Their enzymatic cross-linking by transglutaminase (TGase) allow a modification of their characteristics. The aim of this work is to determine the impact of this modification on their characteristics (size and elastic properties) in a native liquid environment by atomic force microscopy (AFM). The challenge is to immobilize the particles on a surface in their natural state in order to investigate the effect of covalent cross-linking in a simulated milk ultrafiltrate (SMUF).

Commentaires: le titre est différent sur site de la conférence Elsevier "Investigation of properties of casein micelles depleted in beta casein by atomic force microscopy performed in liquid environment"

Ref HAL: hal-01218876_v1
Ref Arxiv: 1504.06221
DOI: 10.1080/00268976.2015.1039089
WoS: 000362544000038
Ref. & Cit.: NASA ADS
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6 Citations
Résumé:

We perform Monte-Carlo simulations to analyse the structure and microscopic dynamics of a viscous Lennard-Jones liquid coupled to a quenched reference configuration of the same liquid. The coupling between the two replicas is introduced via a field epsilon conjugate to the overlap Q between the two particle configurations. This allows us to study the evolution of various static and dynamic correlation functions across the (epsilon, T) equilibrium phase diagram. As the temperature is decreased, we identify increasingly marked precursors of a first-order phase transition between a low-Q and a high-Q phase induced by the field epsilon. We show in particular that both static and dynamic susceptibilities have a maximum at a temperature-dependent value of the coupling field, which defines a `Widom line'. We also show that, in the high-overlap regime, diffusion and structural relaxation are strongly decoupled because single particle motion mostly occurs via discrete hopping on the sites defined by the reference configuration. These results, obtained using conventional numerical tools, provide encouraging signs that an equilibrium phase transition exists in coupled viscous liquids, but also demonstrate that important numerical challenges must be overcome to obtain more conclusive numerical evidence.

Commentaires: 14 pages, 8 figures. Accepted for publication in Molecular Physics (Special Issue in honour of J.-P. Hansen). Réf Journal: Mol. Physics 113, 2707 (2015)

Ref HAL: hal-01216561_v1
DOI: 10.1038/ncomms9121
WoS: 000362949100009
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15 Citations
Résumé:

Spin noise spectroscopy is an optical technique which can probe spin resonances non-perturbatively. First applied to atomic vapours, it revealed detailed information about nuclear magnetism and the hyperfine interaction. In solids, this approach has been limited to carriers in semiconductor heterostructures. Here we show that atomic-like spin fluctuations of Mn ions diluted in CdT e (bulk and quantum wells) can be detected through the Kerr rotation associated to excitonic transitions. Zeeman transitions within and between hyperfine multiplets are clearly observed in zero and small magnetic fields and reveal the local symmetry because of crystal field and strain. The linewidths of these resonances are close to the dipolar limit. The sensitivity is high enough to open the way towards the detection of a few spins in systems where the decoherence due to nuclear spins can be suppressed by isotopic enrichment, and towards spin resonance microscopy with important applications in biology and materials science.