Ref HAL: hal-04931333_v1
DOI: 10.1038/s41586-024-08514-6
Exporter : BibTex | endNote

Ref HAL: hal-04888327_v1
DOI: 10.1063/5.0243331
Exporter : BibTex | endNote
Résumé:

Liquid water still remains an ubiquitous liquid the molecular organization of which requires careful investigation. In this work, we present a study of the second harmonic scattering (SHS) intensity for two different scattering angles, namely the forward and the right angle geometries.This method performed at optical wavelengths is indeed selective towards long correlation lengths. A polarization analysis demonstrates that it is then possible to clearly evidence a coherent component to the total SHS intensity using a fast Fourier transform analysis of the SHS intensity as a function of the fundamental angle of polarization despite its weak relative contribution.A model is then derived based on the rotational invariants to fully unravel the different contributions to the SHS intensity for the two right angle and forward angles of scattering as well as the dependence with the fundamental beam polarization angle. This model fully supports the experimental results further confirming an azimuthal geometry of the water-water orientational correlation function in neat water.

Ref HAL: hal-04877939_v1
Exporter : BibTex | endNote

Ref HAL: hal-04860192_v1
DOI: 10.1016/j.ijheatmasstransfer.2024.126645
Exporter : BibTex | endNote
Résumé:

Near-field radiative heat transfer (RHT) can surpass Planck's blackbody limit by several orders of magnitude due to the tunneling effect of thermal photons. The ability to understand and regulate RHT is of great significance in contactless energy transfer. In this work, we construct a rotating system with a hexagonal boron nitride (h-BN) cylinder for actively regulating the RHT between two nanoparticles (NPs). The results show that when the two NPs are located directly above the cylinder, energy can be directionally transmitted along the cylindrical channel in the form of low-loss surface waves, which can significantly enhance RHT. In addition, we find that the RHT can be regulated by actively manipulating the excitation of cylindrical surface modes. When the rotation point is located in the middle of the line connecting the two NPs, the modulation contrast approaches five orders of magnitude, higher than that of cylinders made of other materials under the same conditions. When its diameter is slightly less than the distance between NPs, the h-BN cylinder shows excellent tunability in the heat exchange. The present work may offer a theoretical possibility for actively regulating and controlling near-field RHT between arbitrary objects based on cylindrical waveguides.

Ref HAL: hal-04891856_v1
Ref Arxiv: 2412.09473
Ref INSPIRE: 2858867
DOI: 10.22323/1.473.0042
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

A future multi-TeV muon collider would provide an important probe for Majorana neutrinos. A muon collider with a collision energy of $\sim$30 TeV would be sensitive to $\nu_e-\nu_\mu$ transition dipole moments of the order of $\sim 10^{-12}\mu_B$ and would be thus competitive with the latest astrophysical observation and laboratory experiments. Contrary to the latter, the muon collider would have the unique advantage of a direct and clean identification of lepton number and flavour violation. This would establish the Majorana nature of the neutrino and would provide crucial complementary information on the neutrino properties in the event of a (near) future observation at low-energy experiments. Additionally, a muon collider would improve by orders of magnitude the direct bounds on the Majorana neutrino mass matrix entries $m_{e\mu}$ and $m_{\mu\mu}$.

Ref HAL: hal-04854424_v1
DOI: 10.1016/B978-0-443-29116-6.00001-1
Exporter : BibTex | endNote
Résumé:

This chapter addresses scattering from suspensions of interacting colloids at finite concentrations, from both a theoretical and an experimental perspective. We start in Section 2 by describing the main effective interactions arising in colloidal systems: excluded volume effects as in hard particle suspensions, electrostatic contributions due to charge dissociation and release of counter-ions, and depletion interactions. We then discuss in Section 3 the Ornstein–Zernike equation, which allows one to calculate the radial distribution function and static structure factor directly from the interaction potential, by using a so-called closure relation. After introducing the most popular closures, we examine their predictions for the equation of state and the problem of thermodynamic consistency. We then briefly tackle the extension of the treatment to mixtures and polydisperse particles. Next, in Section 4 we introduce the ideal Mode-Coupling Theory of the glass transition, a microscopic theory that allows one to predict dynamics solely from the knowledge of the structure. In Section 5, we discuss the main experimental challenges that arise in scattering studies of non-ergodic systems, for which the usual time average performed in experiments does not yield the desired ensemble average. Various schemes proposed for collecting ensemble-averaged data are presented, including multi-speckle methods that allow for time- and space-resolved dynamic light scattering. In Section 6, we illustrate the concepts presented in the first part of the chapter by presenting some key experimental results for colloidal glasses and gels. We start by discussing repulsive hard and soft glasses. Then, we focus on short-ranged attractive colloids and discuss them in the context of attractive glasses as well as gels, highlighting the comparison between theoretical predictions and experimental results. In the final section, we draw some conclusions and make remarks for future work.

Ref HAL: hal-04850843_v1
Ref Arxiv: 2412.11887
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé:

The Ni-Au-Ga interdiffusion mechanisms taking place during rapid thermal annealing (RTA) under oxygen atmosphere of a Ni-Au/p-GaN contact are investigated by high-resolution transmission electron microscopy (HR-TEM) coupled to energy dispersive X-ray spectroscopy (EDX). It is shown that oxygen-assisted, Ni diffusion to the top surface of the metallic contact through the formation of a nickel oxide (NiOx) is accompanied by Au diffusion down to the GaN surface, and by Ga out-diffusion through the GaN/metal interface. Electrical characterizations of the contact by Transmission Line Method (TLM) show that an ohmic contact is obtained as soon as a thin, Au-Ga interfacial layer is formed, even after complete diffusion of Ni or NiOx to the top surface of the contact. Our results clarify that the presence of Ni or NiOx at the interface is not the main origin of the ohmic-like behavior in such contacts. Auto-cleaning of the interface during the interdiffusion process may play a role, but TEM-EDX analysis evidences that the creation of Ga vacancies associated to the formation of a Ga-Au interfacial layer is crucial for reducing the Schottky barrier height, and maximizing the amount of current flowing through the contact.