References of "Verstraete, Matthieu"      in Complete repository Arts & humanities   Archaeology   Art & art history   Classical & oriental studies   History   Languages & linguistics   Literature   Performing arts   Philosophy & ethics   Religion & theology   Multidisciplinary, general & others Business & economic sciences   Accounting & auditing   Production, distribution & supply chain management   Finance   General management & organizational theory   Human resources management   Management information systems   Marketing   Strategy & innovation   Quantitative methods in economics & management   General economics & history of economic thought   International economics   Macroeconomics & monetary economics   Microeconomics   Economic systems & public economics   Social economics   Special economic topics (health, labor, transportation…)   Multidisciplinary, general & others Engineering, computing & technology   Aerospace & aeronautics engineering   Architecture   Chemical engineering   Civil engineering   Computer science   Electrical & electronics engineering   Energy   Geological, petroleum & mining engineering   Materials science & engineering   Mechanical engineering   Multidisciplinary, general & others Human health sciences   Alternative medicine   Anesthesia & intensive care   Cardiovascular & respiratory systems   Dentistry & oral medicine   Dermatology   Endocrinology, metabolism & nutrition   Forensic medicine   Gastroenterology & hepatology   General & internal medicine   Geriatrics   Hematology   Immunology & infectious disease   Laboratory medicine & medical technology   Neurology   Oncology   Ophthalmology   Orthopedics, rehabilitation & sports medicine   Otolaryngology   Pediatrics   Pharmacy, pharmacology & toxicology   Psychiatry   Public health, health care sciences & services   Radiology, nuclear medicine & imaging   Reproductive medicine (gynecology, andrology, obstetrics)   Rheumatology   Surgery   Urology & nephrology   Multidisciplinary, general & others Law, criminology & political science   Civil law   Criminal law & procedure   Criminology   Economic & commercial law   European & international law   Judicial law   Metalaw, Roman law, history of law & comparative law   Political science, public administration & international relations   Public law   Social law   Tax law   Multidisciplinary, general & others Life sciences   Agriculture & agronomy   Anatomy (cytology, histology, embryology...) & physiology   Animal production & animal husbandry   Aquatic sciences & oceanology   Biochemistry, biophysics & molecular biology   Biotechnology   Entomology & pest control   Environmental sciences & ecology   Food science   Genetics & genetic processes   Microbiology   Phytobiology (plant sciences, forestry, mycology...)   Veterinary medicine & animal health   Zoology   Multidisciplinary, general & others Physical, chemical, mathematical & earth Sciences   Chemistry   Earth sciences & physical geography   Mathematics   Physics   Space science, astronomy & astrophysics   Multidisciplinary, general & others Social & behavioral sciences, psychology   Animal psychology, ethology & psychobiology   Anthropology   Communication & mass media   Education & instruction   Human geography & demography   Library & information sciences   Neurosciences & behavior   Regional & inter-regional studies   Social work & social policy   Sociology & social sciences   Social, industrial & organizational psychology   Theoretical & cognitive psychology   Treatment & clinical psychology   Multidisciplinary, general & others     Showing results 1 to 20 of 69 1 2 3 4     Coupled Boltzmann Equation Solver: Effects of the Electron-Phonon Interaction on the Transport CoefficientsPike, Nicholas ; Dewandre, Antoine ; Verstraete, Matthieu Scientific conference (2016, September 22)Recent experimental and theoretical calculations point to a complex interplay between the electron and phonon baths in a wide variety of materials [1,2]. We propose a method of coupling the Boltzmann ... [more ▼]Recent experimental and theoretical calculations point to a complex interplay between the electron and phonon baths in a wide variety of materials [1,2]. We propose a method of coupling the Boltzmann equations for the electron and phonon baths within the relaxation time approximation which we use to calculate the thermoelectric transport coefficients. Our model for the coupled Boltzmann Equation solver includes analytic models, including ${\bf k \cdot p}$ Hamiltonians and tight-binding Hamiltonians, for both the electron and phonon energies and analytic models for the electron and phonon relaxation mechanisms. From these calculations we hope to better understand the role and interplay of electron-phonon and phonon-phonon interactions on the thermoelectric transport coefficients. [1] - Phys. Rev. Lett. ${\bf 114}$, 115901 (2015). [2] - PNAS ${\bf 112}$, 14777-14782 (2015). [less ▲]Detailed reference viewed: 137 (3 ULg) Competition of phonon and magnon effects in the temperature dependence of spinwave stiffnessOstler, Thomas ; Verstraete, Matthieu ; Di Gennaro, Marco et alConference (2016, September 21)Magnons are the elementary magnetic excitations in ordered solids. Understanding such collective excitations is important for a number of technologically relevant fields, such as, magnonics [1] or spin ... [more ▼]Magnons are the elementary magnetic excitations in ordered solids. Understanding such collective excitations is important for a number of technologically relevant fields, such as, magnonics [1] or spin caloritronics [2]. The central interactions in spin caloritronics are the couplings of phonons with electrons and spin degrees of freedom. Furthermore, understanding the effects of temperature on the phonon and spin degrees of freedom adds a further complexity. In the present work we have developed a multiscale model of ferromagnetic materials and demonstrate the effect of temperature dependent phonon displacements on the magnons spectra. Our results show that the for Fe and Ni the effect of phonon displacements acts to reduce the Curie temperature, whereas for Permalloy the opposite is true due to an increased long-ranged exchange interaction. This increased exchange interaction results in an increasing spin-wave stiffness with increasing temperature, overcoming the usual decrease due to magnon softening. To determine the effects of increasing the phonon temperature we have developed a multiscale model whereby we begin by calculating the thermal displacement of phonons, $\sqrt{\langle u^2(T) \rangle}$, calculated using the phonopy software package [3] using electronic ground state and phonon properties determined using the ABINIT software package [4]. Then the exchange constants are determined using the SPRKKR package [5]. Finally, we use linear spin wave theory to determine the effect of the phonon temperature on the exchange alone, demonstrating an increasing frequency of the acoustic magnon branch. We take into account the thermal effects of the magnetic system through the use of the atomistic spin dynamics approach. Magnon softening due to thermal effects demonstrates a more modest increase in the exchange stiffness (over the purely phononic effect), however, an overall increase is still observed. \newline \newline [1] A. V. Chumak, V. I. Vasyuchka, A. A. Serga, and B. Hillebrands, Nature Physics, {\bf 11}, 453–461 (2015). \newline [2] G. E. W. Bauer, E. Saitoh, and B. J. van Wees, Nature Materials {\bf 11}, 391 (2012). \newline [3] Atsushi Togo and Isao Tanaka, Scr. Mater., {\bf 108}, 1-5 (2015) \newline [4] X. Gonze \textit{et al.} Computer Physics Communications {\bf 180}, 2582-2615 (2009). \newline [5] T. Huhne \textit{at al.} Physical Review B, {\bf 58}, 10236 (1998). [less ▲]Detailed reference viewed: 137 (3 ULg) Vibrations in the Flat Land- A Study of the Vibrational Properties of the Transition-Metal DichalcogenidesPike, Nicholas ; Dewandre, Antoine ; Verstraete, Matthieu et alScientific conference (2016, September 03)Calculations of the vibrational properties of the transition-metal dichalcoginides depend critically on the lattice parameters, symmetries of the underlying system, and the non-local dispersive ... [more ▼]Calculations of the vibrational properties of the transition-metal dichalcoginides depend critically on the lattice parameters, symmetries of the underlying system, and the non-local dispersive interaction. Here we present phonon band structure calculations, dielectric tensors, elastic tensors, and Born Effective Charges for the transition-metal dichalcogenides $MoS_2$, $MoSe_2$, $MoTe_2$, $WS_2$, $WSe_2$, $NbS_2$, and $NbSe_2$. We systematically investigate the role of the long-range $e^⁻$-$e^⁻$ interaction, spin-orbit coupling, and pseudo-potential approximation, and highlight their importance on the TMD structural and vibrational properties. We find that the phonon spectrum, calculated with the help of a Grimme's D3 non-local Van der Waals interaction depends strongly on the accuracy of the lattice parameters and slightly on the addition of the non-local Van der Waals interaction in the phonon frequency itself. We also find that the sign of the Born Effective Charges on each atom in the Hexagonal TMDs are the opposite of similarly structured compounds. We explore reasons as to why this occurs. Additionally, our calculation of the dielectric tensor and elastic tensor allow us to describe the mechanical properties of the system which are necessary to know for future device applications. [less ▲]Detailed reference viewed: 434 (0 ULg) Boltzmann Transport Calculations in Systems with Electron-phonon CouplingPike, Nicholas ; Dewandre, Antoine ; Di Gennaro, Marco et alScientific conference (2016, June 07)Recent experimental and theoretical calculations point to a complex interplay between the electron and phonon baths in a wide variety of materials [1,2]. We propose a method of coupling the Boltzmann ... [more ▼]Recent experimental and theoretical calculations point to a complex interplay between the electron and phonon baths in a wide variety of materials [1,2]. We propose a method of coupling the Boltzmann equations for the electron and phonon baths within the relaxation time approximation to describe the changes in the electron and phonon distributions and thus calculate the thermoelectric transport coefficients. Our model for the coupled system will include tight-binding and ${\bf k \cdot p}$ Hamiltonians for both the electron and phonon energies and analytic calculations for the electron and phonon relaxation mechanisms. From these calculations we hope to better understand the role and interplay of electron-phonon and phonon-phonon interactions on the thermoelectric transport coefficients. [1] - Phys. Rev. Lett. ${\bf 114}$, 115901 (2015). [2] - PNAS ${\bf 112}$, 14777-14782 (2015). [less ▲]Detailed reference viewed: 131 (5 ULg) Coupling the Electron and Phonon Baths via the Boltzmann Transport EquationsPike, Nicholas ; Dewandre, Antoine ; Di Gennaro, Marco et alPoster (2016, April 03)Detailed reference viewed: 99 (6 ULg) Ab initio phonon limited transportVerstraete, Matthieu Speech/Talk (2016)We revisit the thermoelectric (TE) transport properties of two champion materials, PbTe and SnSe, using fully first principles methods. In both cases the performance of the material is due to subtle ... [more ▼]We revisit the thermoelectric (TE) transport properties of two champion materials, PbTe and SnSe, using fully first principles methods. In both cases the performance of the material is due to subtle combinations of structural effects, scattering, and phase space reduction. In PbTe anharmonic effects are completely opposite to the predicted quasiharmonic evolution of phonon frequencies and to frequently (and incorrectly) cited extrapolations of experiments. This stabilizes the material at high T, but also tends to enhance its thermal conductivity, in a non linear manner, above 600 Kelvin. This explains why PbTe is in practice limited to room temperature applications. SnSe has recently been shown to be the most efficient TE material in bulk form. This is mainly due to a strongly enhanced carrier concentration and electrical conductivity, after going through a phase transition from 600 to 800 K. We calculate the transport coefficients as well as the defect concentrations ab initio, showing excellent agreement with experiment, and elucidating the origin of the double phase transition as well as the new charge carriers. AH Romero, EKU Gross, MJ Verstraete, and O Hellman PRB 91, 214310 (2015) O. Hellman, IA Abrikosov, and SI Simak, PRB 84 180301 (2011) [less ▲]Detailed reference viewed: 99 (2 ULg) Electron Transport Calculations and Thermoelectric Coefficients of Doped InSbPike, Nicholas ; Di Gennaro, Marco ; Verstraete, Matthieu et alPoster (2016, January 11)Detailed reference viewed: 89 (3 ULg) Strain-induced effects in the electronic and spin properties of a monolayer of ferromagnetic GdAg2Correa, A.; Xu, Bin ; Verstraete, Matthieu et alin Nanoscale (2016), 8Detailed reference viewed: 34 (0 ULg) Quasi-One-Dimensional Metal-Insulator Transitions in Compound Semiconductor SurfacesZhao, J. Z.; Fan, W.; Verstraete, Matthieu et alin Physical Review Letters (2016), 117Detailed reference viewed: 59 (2 ULg) First-Principles Study of the Thermoelectric Properties of SrRuO3Miao, Naihua; Xu, Bin ; Bristowe, Nicholas et alin Journal of Physical Chemistry (2016), 120Detailed reference viewed: 103 (6 ULg) High Temperature Ferromagnetism in a GdAg2 MonolayerOrmaza, M.; Fernandez, L.; Ilyn, M. et alin Nano Letters (2016), 0(0), Detailed reference viewed: 82 (3 ULg) Non-monotonous anisotropy in charge conduction induced by antiferrodistortive transition in metallic SrTiO3Tao, Qian; Loret, Bastien; Xu, Bin et alin Physical Review B (2016), 94Detailed reference viewed: 102 (7 ULg) Recent developments in the ABINIT software packageGonze, X.; Jollet, F.; Araujo, F. Abreu et alin Computer Physics Communications (2016), 205Detailed reference viewed: 84 (3 ULg) Thermoelectric properties of the unfilled skutterudite FeSb3 from first principles and Seebeck local probesLemal, Sébastien ; Ngoc, Nguyen; de Boor, Johannes et alin Physical Review. B: Condensed Matter and Materials Physics (2015), 92Using a combination of first-principles calculations and experimental transport measurements, we study the electronic and magnetic structure of the unfilled skutterudite FeSb3. We employ the hybrid ... [more ▼]Using a combination of first-principles calculations and experimental transport measurements, we study the electronic and magnetic structure of the unfilled skutterudite FeSb3. We employ the hybrid functional approach for exchange-correlation. The ground state is determined to be anti-ferromagnetic with an atomic magnetic moment of 1.6 μB/Fe. The Néel temperature Tn is estimated at 6 K, in agreement with experiments which found a paramagnetic state down to 10 K. The ground state is semiconducting, with a small electronic gap of 33 meV, also consistent with previous experiments on films. Charge carrier concentrations are estimated from Hall resistance measurements. The Seebeck coefficient is measured and mapped using a scanning probe at room temperature that yields an average value of 38.6 μV/K, slightly lower than the theoretical result. The theoretical conductivity is analyzed as a function of temperature and concentration of charge carriers. [less ▲]Detailed reference viewed: 166 (22 ULg) Temperature dependence of the electronic structure of semiconductors and insulatorsPoncé, S.; Gillet, Y.; Laflamme Janssen, J. et alin Journal of Chemical Physics (2015), 143(10), Detailed reference viewed: 82 (1 ULg) Computational benchmarking for ultrafast electron dynamics: wavefunction methods vs density functional theoryOliveira, Micael J. T.; Mignolet, Benoît ; Kus, Tomasz et alin Journal of Chemical Theory and Computation (2015), 11Detailed reference viewed: 120 (0 ULg) Thermal conductivity in PbTe from first principlesRomero, A. H.; Gross, E. K. U.; Verstraete, Matthieu et alin Physical Review B (2015), 91(21), 214310Detailed reference viewed: 151 (0 ULg) Real-space grids and the Octopus code as tools for the development of new simulation approaches for electronic systemsAndrade, Xavier; Strubbe, David; De Giovannini, Umberto et alin Physical Chemistry Chemical Physics (2015)Detailed reference viewed: 111 (0 ULg) Correction to Aluminum Conducts Better than Copper at the Atomic Scale: A First-Principles Study of Metallic Atomic WiresSimbeck, Adam J.; Lanzillo, Nick; Kharche, Neerav et alin ACS nano (2015), 9(6), 6635--6635Detailed reference viewed: 107 (0 ULg) Ab-initio Study of FerecrystalsDewandre, Antoine ; Verstraete, Matthieu Poster (2014, September)Ferecrystals are a new family of compounds first synthesized in 2007 by the group of D. Johnson at the University of Oregon. These materials consist of inter-growths of dichalcogenide and chalcogenide ... [more ▼]Ferecrystals are a new family of compounds first synthesized in 2007 by the group of D. Johnson at the University of Oregon. These materials consist of inter-growths of dichalcogenide and chalcogenide layers, and can be written as [(M X)_{1+δ} ]_m [T X_2 ]_n where M = Sn, Pb, Sb, Ni and some rare earths; T = Ti, V, Cr, Nb and Ta; X= S and Se. The integers m and n denote the numbers of consecutive formula unit layers in the different components of the inter-growth. The δ parameter reflects the difference of the in-plane cell constants between components of the inter-growth. This family of nanostructured materials shows promising properties for thermoelectric devices. The compounds studied here are [(SnSe)_1.29 ]_{234} [M oSe_2 ]_1 . We performed structural characterisation and examined the transfer of charge at the interface between the two materials. We show that there is a depletion of charge at the interface between the two compo- nents of the heterostructures and that structural distortions of the SnSe layers in the supercell are similar to those observed in slab calculations. [less ▲]Detailed reference viewed: 150 (7 ULg) 1 2 3 4