Hot electron cooling by acoustic phonons in graphene

We have investigated the energy loss of hot electrons in metallic graphene by means of GHz noise thermometry at liquid helium temperature. We observe the electronic temperature T / V at low bias in agreement with the heat diffusion to the leads described by the Wiedemann-Franz law. We report on $T\propto\sqrt{V}$ behavior at high bias, which corresponds to a T4 dependence of the cooling power. This is the signature of a 2D acoustic phonon cooling mechanism. From a heat equation analysis of the two regimes we extract accurate values of the electron-acoustic phonon coupling constant $\Sigma$ in monolayer graphene. Our measurements point to an important effect of lattice disorder in the reduction of $\Sigma$, not yet considered by theory. Moreover, our study provides a strong and firm support to the rising field of graphene bolometric detectors.Comment: 5 figure

Entanglement in Coupled Harmonic Oscillators via Unitary Transformation

We develop an approach to study the entanglement in two coupled harmonic oscillators. We start by introducing an unitary transformation to end up with the solutions of the energy spectrum. These are used to construct the corresponding coherent states through the standard way. To evaluate the degree of the entanglement between the obtained states, we calculate the purity function in terms of the coherent and number states, separately. The result is yielded to two parameters dependance of the purity, which can be controlled easily. Interesting results are derived by fixing the mixing angle of such transformation as \pi/2. We compare our results with already published work and point out the relevance of these findings to a systematic formulation of the entanglement effect in two coupled harmonic oscillators.Comment: 19 pages, 6 figures, clarification and reference added, misprints corrected. Version published in JSTA

Direct transfer and Raman characterization of twisted graphene bilayer

International audienc

Mechanical and thermodynamic properties of rare-earth-based Ni intermetallic compounds crystallized in the C15b structure: an Ab-initio study

International audienceThis study investigates the mechanical properties and structural and thermodynamic stabilities of RENi5 compounds (RE: rare earth metals, with RE = Y, La, and Gd) in the AuBe5 (C15b) structure. Intermetallics of this type have potential applications in hydrogen battery technology, but their properties are not well understood. Using first-principles calculations, we calculated the mechanical properties, including the shear modulus, Young's modulus, bulk modulus, Poisson's ratio, Vickers hardness, and ductility of these compounds. Our calculations revealed that these compounds are both mechanically and thermodynamically stable. Additionally, our results suggest that all compounds are ductile. The YNi5 compound has the highest Debye temperature, indicating greater covalent Y-Ni bonds and greater hardness. We analyzed these findings with respect to the electronic structure of the compounds by calculating the density of states (DOS) and charge density distribution. These insights into the mechanical, thermodynamic, and electronic properties of RENi5 intermetallics can inform the design and development of novel materials with improved properties in hydrogen batteries, mechanical applications or other related fields

Interactions électroniques à l'interface graphène et oxyde cobaltite

National audienc

Interactions électroniques à l'interface graphène et oxyde cobaltite, 2016, ICMS 2016

International audienc

A New Approach for AFM Cantilever Elaboration with 3C-SiC

International audienceThe recent achievement of a continuous silicon monocrystalline thin film on 3C-SiC epilayers deposited on silicon substrates has opened the field for new microstructures. In this work, this original hetero-structure is the basis for the elaboration of an entire cantilever for atomic force microscopy. The hetero-epitaxially grown silicon layer is used to define the tip of the cantilever fabricated from the 3C-SiC epilayer deposited on silicon. The complete cantilever is elaborated by plasma etching using a nickel mask. The use of a full dry etching process is very promising as it is independent of the crystalline orientation of the silicon epilayer contrary to process based on wet etching solutions. Moreover, based on such hetero-structure, new MEMS devices can be considered

Interactions électroniques à l'interface graphène et oxyde cobaltite

National audienc