The Experts below are selected from a list of 72138 Experts worldwide ranked by ideXlab platform
Michael Thoss - One of the best experts on this subject based on the ideXlab platform.
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resonant electron Transport in single molecule junctions vibrational excitation rectification negative differential resistance and local cooling
Physical Review B, 2011Co-Authors: Rainer Hartle, Michael ThossAbstract:Vibronic eects in resonant electron Transport through single-molecule junctions are analyzed. The study is based on generic models for molecular junctions, which include electronic states on the molecular bridge that are vibrationally coupled and exhibit Coulomb interaction. The Transport calculations employ a master equation approach. The results, obtained for a series of models with increasing complexity, show a multitude of interesting Transport phenomena, including vibrational excitation, rectication, negative dierential resistance (NDR) as well as local cooling. While some of these phenomena have been observed or proposed before, the present analysis extends previous studies and allows a more detailed understanding of the Underlying Transport mechanisms. In particular, it is shown that many of the observed phenomena can only be explained if electronhole pair creation processes at the molecule-lead interface are taken into account. Furthermore, vibronic eects in sytems with multiple electronic states and their role for the stability of molecular
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resonant electron Transport in single molecule junctions vibrational excitation rectification negative differential resistance and local cooling
Physical Review B, 2011Co-Authors: Rainer Hartle, Michael ThossAbstract:Vibronic effects in resonant electron Transport through single-molecule junctions are analyzed. The study is based on generic models for molecular junctions, which include electronic states on the molecular bridge that are vibrationally coupled and exhibit Coulomb interaction. The Transport calculations employ a master equation approach. The results, obtained for a series of models with increasing complexity, show a multitude of interesting Transport phenomena, including vibrational excitation, rectification, negative differential resistance, as well as local cooling. While some of these phenomena have been observed or proposed before, the present analysis extends previous studies and allows a more detailed understanding of the Underlying Transport mechanisms. In particular, it is shown that many of the observed phenomena can only be explained if electron-hole pair creation processes at the molecule-lead interface are taken into account. Furthermore, vibronic effects in systems with multiple electronic states and their role for the stability of molecular junctions are analyzed.
Rainer Hartle - One of the best experts on this subject based on the ideXlab platform.
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resonant electron Transport in single molecule junctions vibrational excitation rectification negative differential resistance and local cooling
Physical Review B, 2011Co-Authors: Rainer Hartle, Michael ThossAbstract:Vibronic eects in resonant electron Transport through single-molecule junctions are analyzed. The study is based on generic models for molecular junctions, which include electronic states on the molecular bridge that are vibrationally coupled and exhibit Coulomb interaction. The Transport calculations employ a master equation approach. The results, obtained for a series of models with increasing complexity, show a multitude of interesting Transport phenomena, including vibrational excitation, rectication, negative dierential resistance (NDR) as well as local cooling. While some of these phenomena have been observed or proposed before, the present analysis extends previous studies and allows a more detailed understanding of the Underlying Transport mechanisms. In particular, it is shown that many of the observed phenomena can only be explained if electronhole pair creation processes at the molecule-lead interface are taken into account. Furthermore, vibronic eects in sytems with multiple electronic states and their role for the stability of molecular
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resonant electron Transport in single molecule junctions vibrational excitation rectification negative differential resistance and local cooling
Physical Review B, 2011Co-Authors: Rainer Hartle, Michael ThossAbstract:Vibronic effects in resonant electron Transport through single-molecule junctions are analyzed. The study is based on generic models for molecular junctions, which include electronic states on the molecular bridge that are vibrationally coupled and exhibit Coulomb interaction. The Transport calculations employ a master equation approach. The results, obtained for a series of models with increasing complexity, show a multitude of interesting Transport phenomena, including vibrational excitation, rectification, negative differential resistance, as well as local cooling. While some of these phenomena have been observed or proposed before, the present analysis extends previous studies and allows a more detailed understanding of the Underlying Transport mechanisms. In particular, it is shown that many of the observed phenomena can only be explained if electron-hole pair creation processes at the molecule-lead interface are taken into account. Furthermore, vibronic effects in systems with multiple electronic states and their role for the stability of molecular junctions are analyzed.
Johannes Gooth - One of the best experts on this subject based on the ideXlab platform.
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thermal and electrical signatures of a hydrodynamic electron fluid in tungsten diphosphide
Nature Communications, 2018Co-Authors: Johannes Gooth, Robert Zierold, Ute Drechsler, Fabian Menges, N Kumar, Vicky Suβ, Chandra Shekhar, Claudia FelserAbstract:In stark contrast to ordinary metals, in materials in which electrons strongly interact with each other or with phonons, electron Transport is thought to resemble the flow of viscous fluids. Despite their differences, it is predicted that Transport in both conventional and correlated materials is fundamentally limited by the uncertainty principle applied to energy dissipation. Here we report the observation of experimental signatures of hydrodynamic electron flow in the Weyl semimetal tungsten diphosphide. Using thermal and magneto-electric Transport experiments, we find indications of the transition from a conventional metallic state at higher temperatures to a hydrodynamic electron fluid below 20 K. The hydrodynamic regime is characterized by a viscosity-induced dependence of the electrical resistivity on the sample width and by a strong violation of the Wiedemann–Franz law. Following the uncertainty principle, both electrical and thermal Transport are bound by the quantum indeterminacy, independent of the Underlying Transport regime.
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Electrical and Thermal Transport at the Planckian Bound of Dissipation in the Hydrodynamic Electron Fluid of WP2
arXiv, 2017Co-Authors: Johannes Gooth, Robert Zierold, Ute Drechsler, Vladimír Süss, Fabian Menges, Chander Shekhar, Y. Sun, N Kumar, Claudia Felser, Bernd GotsmannAbstract:Materials with strongly-correlated electrons exhibit interesting phenomena such as metal-insulator transitions and high-temperature superconductivity. In stark contrast to ordinary metals, electron Transport in these materials is thought to resemble the flow of viscous fluids. Despite their differences, it is predicted that Transport in both, conventional and correlated materials, is fundamentally limited by the uncertainty principle applied to energy dissipation. Here we discover hydrodynamic electron flow in the Weyl-semimetal tungsten phosphide (WP2). Using thermal and magneto-electric Transport experiments, we observe the transition from a conventional metallic state, at higher temperatures, to a hydrodynamic electron fluid below 20 K. The hydrodynamic regime is characterized by a viscosity-induced dependence of the electrical resistivity on the square of the channel width, and by the observation of a strong violation of the Wiedemann-Franz law. From magneto-hydrodynamic experiments and complementary Hall measurements, the relaxation times for momentum and thermal energy dissipating processes are extracted. Following the uncertainty principle, both are limited by the Planckian bound of dissipation, independent of the Underlying Transport regime.
Vo Anh - One of the best experts on this subject based on the ideXlab platform.
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numerical methods and analysis for a multi term time space variable order fractional advection diffusion equations and applications
Journal of Computational and Applied Mathematics, 2019Co-Authors: Ruige Chen, Vo Anh, Fawang LiuAbstract:Field experiments of solute Transport through heterogeneous porous and fractured media show that the growth of contaminant plumes may convert between diffusive states. In this paper, we propose a multi-term time–space variable-order fractional advection–diffusion model (MTT-SVO-FADM) to describe the Underlying Transport dynamics. We consider a numerical approach based on the implicit numerical method for numerical solution of this model. A fully-discrete numerical scheme is developed by using the classical finite difference method. The unconditional stability and convergence of the scheme are discussed and theoretically proved. We use a modified grid approximation method (MGAM) to estimate the model’s parameters. The MTT-SVO-FADM is then applied to describe transient dispersion observed at a field tracer test and four numerical experiments. The results show that this model can simulate the experimental data more accurately and can efficiently quantify these transitions.
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Numerical methods and analysis for a multi-term time–space variable-order fractional advection–diffusion equations and applications
'Elsevier BV', 2019Co-Authors: Chen Ruige, Liu Fawang, Vo AnhAbstract:Field experiments of solute Transport through heterogeneous porous and fractured media show that the growth of contaminant plumes may convert between diffusive states. In this paper, we propose a multi-term time–space variable-order fractional advection–diffusion model (MTT-SVO-FADM) to describe the Underlying Transport dynamics. We consider a numerical approach based on the implicit numerical method for numerical solution of this model. A fully-discrete numerical scheme is developed by using the classical finite difference method. The unconditional stability and convergence of the scheme are discussed and theoretically proved. We use a modified grid approximation method (MGAM) to estimate the model's parameters. The MTT-SVO-FADM is then applied to describe transient dispersion observed at a field tracer test and four numerical experiments. The results show that this model can simulate the experimental data more accurately and can efficiently quantify these transitions
Renaud Toussaint - One of the best experts on this subject based on the ideXlab platform.
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relative rates of fluid advection elemental diffusion and replacement govern reaction front patterns
Earth and Planetary Science Letters, 2021Co-Authors: Daniel Koehn, Sandra Piazolo, Nicolas Beaudoin, Ulrich Kelka, Liene Spruženiece, Christine V Putnis, Renaud ToussaintAbstract:Abstract Replacement reactions during fluid infiltration into porous media, rocks and buildings are known to have important implications for reservoir development, ore formation as well as weathering. Natural observations and experiments have shown that in such systems the shape of reaction fronts can vary significantly ranging from smooth, rough to highly irregular. It remains unclear what process-related knowledge can be derived from these reaction front patterns. In this contribution we show a numerical approach to test the effect of relative rates of advection, diffusion, and reaction on the development of reaction fronts patterns in granular aggregates with permeable grain boundaries. The numerical model takes (i) fluid infiltration along permeable grain boundaries, (ii) reactions and (iii) elemental diffusion into account. We monitor the change in element concentration within the fluid, while reactions occur at a pre-defined rate as a function of the local fluid concentration. In non-dimensional phase space using Peclet and Damkohler numbers, results show that there are no rough fronts without advection (Peclet 10−3). As advection becomes more dominant and reaction slower, roughness develops across several grains with a full microstructure mimicking replacement in the most extreme cases. The reaction front patterns show an increase in roughness with increasing Peclet number from Peclet 10 to 100 but then a decrease in roughness towards higher Peclet numbers controlled by the Damkohler number. Our results indicate that reaction rates are crucial for pattern formation and that the shape of reaction fronts is only partly due to the Underlying Transport mechanism.
