Faits marquants 2014

Activation mechanism in the hydrogen storage material MgH2

Hydrogen, produced by electrolysis of water, has huge potential as a sustainable energy carrier for storage of the “green” electricity produced by renewable sources. It can be used in fuel cells or even burnt directly in internal combustion engines. But a major obstacle to the expansion of hydrogen-based technology is the lack of compact and safe storage systems... Full Text

Strain couples a nano-mechanical oscillator and a quantum emitter

In theory, the strangeness of quantum mechanics is not solely restricted to the microscopic world but applies equally to macroscopic objects. However, in practice, to get a macroscopic object to behave quantum mechanically requires an exquisite degree of control over the object and its environment... Full text

Evaporation of helium in a porous material

Porous materials are thirsty materials. Fluids whose liquid phase wets their substrate condense in porous materials at pressures smaller than the saturated vapour pressure, pressures where the bulk stable phase would be gaseous. For water, examples in everyday life range from the silica gels used as desiccants, to wood. Also, unlike in bulk conditions, the transition from gas to liquid shows strong hysteresis... Full text

Bloch-point Domain Walls in cylindrical magnetic nanowires

Current data storage technology relies on storing bits at a surface, using optics (blu-Ray DVDs), electric charges (flash memory) or magnetism (hard disk drives). Progress in storage capacity will soon face a halt, as the shrinking size of individual bits faces fundamental limits... Full text

Superconductivity Dome around a Quantum Critical Point

The interplay between ordered states and the superconductivity that develops when they are destabilized is central in the understanding of subjects as diverse as high temperature superconductors and quantum chromodynamics. In the case of the Heavy Fermion family of compounds, superconductivity develops in a region of the phase diagram enclosed by a dome-shaped boundary... Full text

Mesoscopic spin glasses

A glass is arguably the strangest phase of ordinary matter ; it is neither a liquid nor a crystalline solid, but it has aspects of both. One of the simplest glass structures is the spin-glass. We have started a project aiming at elucidating the physics governing these strange systems using tools coming from another domain of condensed matter physics, namely mesoscopic physics... Full text

At the interface between ab initio calculations and correlated models

Over the last few years, multiferroic compounds have become a hot subject of research. Indeed, the discovery of ”colossal” magneto-electric effects in some of these compounds, i.e. a very large coupling between their electrical and magnetic properties, opens the possibility to control magnetic properties using an electric fi eld and, in return, to control electric properties (polarisation, dielectric constant) by an applied magnetic field... Full Text

New mm-wave instrument (”NIKA”) opens for astronomers

Millimetre-wave astronomy is an important tool for studying the cold and the primordial stages of our Universe. This branch of astronomy presents monumental challenges in detector science and technology. At the NEEL Institute, we have pioneered the development of the Lumped Element Kinetic Inductance Detectors (LEKIDs) technology... Full text

Unravelling structure and magnetism in strongly correlated systems

Doped LaMnO3 compounds are a playground for the study of strong electronic correlations. Their remarkable properties under external magnetic fi eld, such as the giant magneto-resistance in use in magnetic devices, is due to an intricate interplay between lattice, orbital and spin degrees of freedom... Full text

Fibered nano-optical tweezers for micro- and nano-particle trapping

Optical ”tweezers” are a means by which a small particle can be held stably in the electromagnetic fi eld of a light beam. They have been a well established tool for non-invasive manipulation of very small objects in biology, chemistry, and soft-matter physics. In this context we are developing novel tweezers based on two optical-fi bre nano-tips... Full text

Vortex creep in type II superconductors : when vortices cross walls

Perhaps the most striking property of superconductors, after the absence of electrical resistance, is their ability to expel a magnetic field... Full text

Tunable superconductivity in an array of metal dots decorating graphene

Scientists have worked hard in the last few decades to grow nanostructures free of defects. The near-perfect atomic arrangements obtained at the nanometre scale have been employed to create new, efficient devices such as light-emitters, transistors and sensors... Full text

Low temperature damping in a nano-electro-mechanical device

Solid matter can be found in two states depending on the ordering of its atoms : Crystalline solids display a characteristic translational long-range order, whereas amorphous solids lack it. Full text

Tunable light emission from a boron nitride nanotube device

Scientists have worked hard in the last few decades to grow nanostructures free of defects. The near-perfect atomic arrangements obtained at the nanometre scale have been employed to create new, effi cient devices such as light-emitters, transistors and sensors ... Full text

Diamond Schottky diodes for high power electronics

Diamond has a relatively wide bandgap but it can be made into a semiconductor, or even a metal, by doping it with impurity atoms. Semiconducting diamond layers, grown epitaxially on diamond substrates, have outstanding electrical and thermal properties in view of high power applications... Full text

Table-top Helium 3 cryostat

Cryostats that use the rare isotope He3 as cooling fl uid to achieve temperatures below 1 degree K can be very complex to operate. A prototype of a user-friendly, ”table-top” Helium 3 cryostat has been designed and built recently at NEEL Institute in order to satisfy a research team’s needs for frequent electrical characterization measurements at very low temperature ... Full text

The quantum diffusion of muons in the spin ice Dy2Ti2O7

Among the magnetic probes available for studying condensed matter, muon Spin Relaxation (mu-SR) occupies an important place. This technique is highly sensitive to local magnetic fi elds and can probe spin fl uctuations over time scales from roughly 10-5 to 10-12 seconds... Full text

Scanning gate microscopy on a quantum point contact

The electrical conductance through a nanometer-scale constriction in a plane of electrons exhibits quantized values that reveal the quantum properties of the electrons... Full text

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