Institut NÉEL

Présentation

L’institut Néel, UPR 2940, est un laboratoire de recherche fondamentale en physique de la matière condensée, riche d’une importante composante interdisciplinaire aux interfaces avec la chimie, l’ingénierie et la biologie. Organisé en 3 départements en interaction, les 19 équipes de recherche s’appuient sur un socle exceptionnel d’expertises technologiques. Le laboratoire s’implique aussi activement dans la valorisation de ses recherches d’une part par l’intermédiaire de partenariats avec les entreprises et d’autre part grâce à une forte synergie avec le monde universitaire.

Actualité scientifique

L’INP met en ligne l’actualité scientifique "Un système nano-mécanique hybride" , relative à l’article A single nitrogen-vacancy defect coupled to a nanomechanical oscillator,  publié dans Nature Physics.

Fluctuating charge order destroys metallic behavior

Phase transitions are ubiquitous : from the crystallization of water into ice, to the alignment of electron spins inside a magnet, to the emergence of superconductivity in a cooled metal. In the case of continuous, second-order, transitions, the transformation from one phase to the other does not come suddenly : it is generally announced by a strong increase in the fluctuations of an “order parameter”. The most familiar example is the phenomenon of critical opalescence, reflecting the increase in density fluctuations at the approach of the liquid-gas transition. (Full text)

 

Blocking heat transfer at the nanoscale

Phonons are tiny packets of vibrational energy, quanta of vibration of the lattice. When acoustic (i.e. low frequency) phonons propagate, they give rise to thermal conductance, the property of a solid to conduct heat. At room temperature, many phonons are present and they are strongly scattered by each other as well as by electrons or impurities ; the transport is called diffusive. At low temperature, the probability of phonon scattering greatly decreases and, finally, heat transport will be limited only by scattering on the rough surface of the solid. At even lower temperature, the wavelength of phonons becomes so large that the surface behaves like a mirror for them : they undergo specular re$ ection. In this ”ballistic” regime, phonons will conserve their energy until they reach a thermal bath, a large reservoir where they can finally thermalize with their counterparts. (Full text)