The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
D. Van Der Knijff - One of the best experts on this subject based on the ideXlab platform.
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particle unstable and weakly bound light nuclei with a sturmian approach that preserves the Pauli Principle
Nuclear Physics, 2007Co-Authors: L. Canton, G. Pisent, J. P. Svenne, K. Amos, S. Karataglidis, D. Van Der KnijffAbstract:Sturmian theory for nucleon-nucleus scattering is discussed in the presence of all the phenomenological ingredients necessary for the description of weakly-bound (or particle-unstable) light nuclear systems. Currently, we use a macroscopic potential model of collective nature. The analysis shows that the couplings to low-energy collective-core excitations are fundamental but they are physically meaningful only if the constraints introduced by the Pauli Principle are taken into account. The formalism leads one to discuss a new concept, Pauli hindrance, which appears to be important to understand the structure of weakly-bound and unbound systems.
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Particle-unstable and weakly-bound light nuclei with a Sturmian approach that preserves the Pauli Principle
Nuclear Physics A, 2007Co-Authors: L. Canton, G. Pisent, J. P. Svenne, K. Amos, S. Karataglidis, D. Van Der KnijffAbstract:Sturmian theory for nucleon-nucleus scattering is discussed in the presence of all the phenomenological ingredients necessary for the description of weakly-bound (or particle-unstable) light nuclear systems. Currently, we use a macroscopic potential model of collective nature. The analysis shows that the couplings to low-energy collective-core excitations are fundamental but they are physically meaningful only if the constraints introduced by the Pauli Principle are taken into account. The formalism leads one to discuss a new concept, Pauli hindrance, which appears to be important to understand the structure of weakly-bound and unbound systems.Comment: 5 pages, 2 figures, 1 table, contribution to proceedings of "18th International IUPAP Conference on Few-Body Problems in Physics," Santos, Brazil, August 21-26, 200
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Role of the Pauli Principle in collective-model coupled-channel calculations.
Physical review letters, 2005Co-Authors: L. Canton, G. Pisent, J. P. Svenne, D. Van Der Knijff, K. Amos, S. KarataglidisAbstract:A multichannel algebraic scattering theory, to find solutions of coupled-channel scattering problems with interactions determined by collective models, has been structured to ensure that the Pauli Principle is not violated. By tracking the results in the zero coupling limit, a correct interpretation of the subthreshold and resonant spectra of the compound system can be made. As an example, the neutron-12C system is studied defining properties of 13C to 10 MeV excitation. Accounting for the Pauli Principle in collective coupled-channels models is crucial to the outcome.
Steve Arscott - One of the best experts on this subject based on the ideXlab platform.
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effect of the Pauli Principle on photoelectron spin transport in p gaas
Proceedings of SPIE, 2015Co-Authors: F Cadiz, D Paget, A C H Rowe, Lucio Martinelli, Steve ArscottAbstract:ABSTRACT In p + GaAs thin lms, under excitation by a tightly-focussed laser, the sp atial pro le of the spin polarization ismonitored as a function of excitation power. It is found that photo electron di usion depends on spin, as a directconsequence of the Pauli Principle which causes a concentration de pendence of the spin sti ness. Thermoelectriccurrents are also predicted to depend on spin under degeneracy ( spin Soret currents), but these currents play arelatively small role in this case. The spin dependence of the mobility is a lso found weak. Conversely, ambipolarcoupling with holes increases the steady-state photo-electron de nsity at the place of excitation and therefore theamplitude of the degeneracy-induced polarization decrease at the place of excitation.Keywords: Spin transport, di usion, Polarization 1. INTRODUCTION The numerous investigations of spin transport in semiconductors h ave led to the demonstration, amongothers, of various processes which can a ect this transport: i) s pin-charge couplings caused by the spin-orbitinteraction, which may be used to electrically manipulate electronic sp ins in quantum wells
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effect of the Pauli Principle on photoelectron spin transport in p gaas
Physical Review B, 2015Co-Authors: F Cadiz, D Paget, A C H Rowe, Thierry Amand, P. Barate, Steve ArscottAbstract:In ${p}^{+}$ GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly focused light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about $2\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$ from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli Principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photoelectron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and band-gap renormalization are negligible due to electrostatic screening by the hole gas.
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Effect of the Pauli Principle on photoelectron spin transport in p + GaAs
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2015Co-Authors: F Cadiz, D Paget, Alistair Rowe, Thierry Amand, P. Barate, Steve ArscottAbstract:In p+ GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly focused light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about 2μm from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli Principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photoelectron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and band-gap renormalization are negligible due to electrostatic screening by the hole gas.
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Effect of the Pauli Principle on photoelectron spin transport in $p^+$ GaAs
arXiv: Mesoscale and Nanoscale Physics, 2013Co-Authors: F Cadiz, D Paget, Alistair Rowe, Thierry Amand, P. Barate, Steve ArscottAbstract:In p+ GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly-focussed light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about $2 \; \mu m$ from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli Principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photo-electron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currrents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and bandgap renormalization are negligible due to electrostatic screening by the hole gas.
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effect of the Pauli Principle on photoelectron spin transport in p gaas
arXiv: Mesoscale and Nanoscale Physics, 2013Co-Authors: F Cadiz, D Paget, A C H Rowe, Thierry Amand, P. Barate, Steve ArscottAbstract:In p+ GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly-focussed light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about $2 \; \mu m$ from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli Principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photo-electron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currrents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and bandgap renormalization are negligible due to electrostatic screening by the hole gas.
L. Canton - One of the best experts on this subject based on the ideXlab platform.
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particle unstable and weakly bound light nuclei with a sturmian approach that preserves the Pauli Principle
Nuclear Physics, 2007Co-Authors: L. Canton, G. Pisent, J. P. Svenne, K. Amos, S. Karataglidis, D. Van Der KnijffAbstract:Sturmian theory for nucleon-nucleus scattering is discussed in the presence of all the phenomenological ingredients necessary for the description of weakly-bound (or particle-unstable) light nuclear systems. Currently, we use a macroscopic potential model of collective nature. The analysis shows that the couplings to low-energy collective-core excitations are fundamental but they are physically meaningful only if the constraints introduced by the Pauli Principle are taken into account. The formalism leads one to discuss a new concept, Pauli hindrance, which appears to be important to understand the structure of weakly-bound and unbound systems.
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Particle-unstable and weakly-bound light nuclei with a Sturmian approach that preserves the Pauli Principle
Nuclear Physics A, 2007Co-Authors: L. Canton, G. Pisent, J. P. Svenne, K. Amos, S. Karataglidis, D. Van Der KnijffAbstract:Sturmian theory for nucleon-nucleus scattering is discussed in the presence of all the phenomenological ingredients necessary for the description of weakly-bound (or particle-unstable) light nuclear systems. Currently, we use a macroscopic potential model of collective nature. The analysis shows that the couplings to low-energy collective-core excitations are fundamental but they are physically meaningful only if the constraints introduced by the Pauli Principle are taken into account. The formalism leads one to discuss a new concept, Pauli hindrance, which appears to be important to understand the structure of weakly-bound and unbound systems.Comment: 5 pages, 2 figures, 1 table, contribution to proceedings of "18th International IUPAP Conference on Few-Body Problems in Physics," Santos, Brazil, August 21-26, 200
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Role of the Pauli Principle in collective-model coupled-channel calculations.
Physical review letters, 2005Co-Authors: L. Canton, G. Pisent, J. P. Svenne, D. Van Der Knijff, K. Amos, S. KarataglidisAbstract:A multichannel algebraic scattering theory, to find solutions of coupled-channel scattering problems with interactions determined by collective models, has been structured to ensure that the Pauli Principle is not violated. By tracking the results in the zero coupling limit, a correct interpretation of the subthreshold and resonant spectra of the compound system can be made. As an example, the neutron-12C system is studied defining properties of 13C to 10 MeV excitation. Accounting for the Pauli Principle in collective coupled-channels models is crucial to the outcome.
Vinay Ambegaokar - One of the best experts on this subject based on the ideXlab platform.
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decoherence in weak localization i Pauli Principle in influence functional
Physical Review B, 2007Co-Authors: Florian Marquardt, Jan Von Delft, Robert A Smith, Vinay AmbegaokarAbstract:This is the first in a series of two papers, in which we revisit the problem of decoherence in weak localization. The basic challenge addressed in our work is to calculate the decoherence of electrons interacting with a quantum-mechanical environment while taking proper account of the Pauli Principle. First, we review the usual influence functional approach valid for decoherence of electrons due to classical noise, showing along the way how the quantitative accuracy can be improved by properly averaging over closed (rather than unrestricted) random walks. We then use a heuristic approach to show how the Pauli Principle may be incorporated into a path-integral description of decoherence in weak localization. This is accomplished by introducing an effective modification of the quantum noise spectrum, after which the calculation proceeds analogous to the case of classical noise. Using this simple but efficient method, which is consistent with much more laborious diagrammatic calculations, we demonstrate how the Pauli Principle serves to suppress the decohering effects of quantum fluctuations of the environment, and essentially confirm the classic result of Altshuler, Aronov, and Khmelnitskii [J. Phys. C 15, 7367 (1982)] for the energy-averaged decoherence rate, which vanishes at zero temperature. Going beyond that, we employ our method to calculate explicitly the leading quantum corrections to the classical decoherence rates and to provide a detailed analysis of the energy dependence of the decoherence rate. The basic idea of our approach is general enough to be applicable to the decoherence of degenerate Fermi systems in contexts other than weak localization as well. Paper II will provide a more rigorous diagrammatic basis for our results by rederiving them from a Bethe-Salpeter equation for the Cooperon.
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Decoherence in weak localization. I. Pauli Principle in influence functional
Physical Review B, 2007Co-Authors: Florian Marquardt, Jan Von Delft, Robert A Smith, Vinay AmbegaokarAbstract:This is the first in a series of two papers (I and II), in which we revisit the problem of decoherence in weak localization. The basic challenge addressed in our work is to calculate the decoherence of electrons interacting with a quantum-mechanical environment, while taking proper account of the Pauli Principle. First, we review the usual influence functional approach valid for decoherence of electrons due to classical noise, showing along the way how the quantitative accuracy can be improved by properly averaging over closed (rather than unrestricted) random walks. We then use a heuristic approach to show how the Pauli Principle may be incorporated into a path-integral description of decoherence in weak localization. This is accomplished by introducing an effective modification of the quantum noise spectrum, after which the calculation proceeds in analogy to the case of classical noise. Using this simple but efficient method, which is consistent with much more laborious diagrammatic calculations, we demonstrate how the Pauli Principle serves to suppress the decohering effects of quantum fluctuations of the environment, and essentially confirm the classic result of Altshuler, Aronov and Khmelnitskii for the energy-averaged decoherence rate, which vanishes at zero temperature. Going beyond that, we employ our method to calculate explicitly the leading quantum corrections to the classical decoherence rates, and to provide a detailed analysis of the energy-dependence of the decoherence rate. The basic idea of our approach is general enough to be applicable to decoherence of degenerate Fermi systems in contexts other than weak localization as well. -- Paper II will provide a more rigorous diagrammatic basis for our results, by rederiving them from a Bethe-Salpeter equation for the Cooperon.Comment: 27 pages, 8 figures. This is the first of a series of two papers on decoherence. It introduces an influence functional approach. The second paper obtains equivalent results using a diagrammatic Bethe-Salpeter equation. For a concise summary of the main results and conclusions, see Section II of the first pape
F Cadiz - One of the best experts on this subject based on the ideXlab platform.
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effect of the Pauli Principle on photoelectron spin transport in p gaas
Proceedings of SPIE, 2015Co-Authors: F Cadiz, D Paget, A C H Rowe, Lucio Martinelli, Steve ArscottAbstract:ABSTRACT In p + GaAs thin lms, under excitation by a tightly-focussed laser, the sp atial pro le of the spin polarization ismonitored as a function of excitation power. It is found that photo electron di usion depends on spin, as a directconsequence of the Pauli Principle which causes a concentration de pendence of the spin sti ness. Thermoelectriccurrents are also predicted to depend on spin under degeneracy ( spin Soret currents), but these currents play arelatively small role in this case. The spin dependence of the mobility is a lso found weak. Conversely, ambipolarcoupling with holes increases the steady-state photo-electron de nsity at the place of excitation and therefore theamplitude of the degeneracy-induced polarization decrease at the place of excitation.Keywords: Spin transport, di usion, Polarization 1. INTRODUCTION The numerous investigations of spin transport in semiconductors h ave led to the demonstration, amongothers, of various processes which can a ect this transport: i) s pin-charge couplings caused by the spin-orbitinteraction, which may be used to electrically manipulate electronic sp ins in quantum wells
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Spin dependent electron transport in semiconductors due to the Pauli Principle
2015Co-Authors: F CadizAbstract:This thesis is concerned with transport of photoinjected minority spin-polarized electrons in doped semiconductors, as a function of both the density and the temperature of the injected electron gas. In p-GaAs thin films, charge and spin transport is investigated theoretically and experimentally by using a novel polarized microphotoluminescence (µPL) technique which consists in imaging the spatially-resolved PL intensity and polarization under a tightly-focused circularly-polarized CW laser excitation. Study of the experimental profiles at low concentration and under an applied electric field shows that the minority electron mobility is mainly determined by the electron temperature instead of the majority hole statistics, introducing a puzzling piece to the current understanding of scattering processes in semiconductors. At higher densities, this experimental technique has allowed us to explore a novel charge-spin coupling mechanism which modifies electron transport. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the centre of the spin polarization profile appears with a polarization maximum at a distance of about r= 2 µm from the excitation. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli Principle which causes in general a concentration dependence of the spin stiffness. This results in a novel spin filter effect in an homogeneous material. The other effects which may modify spin transport in a degenerate electron gas are thermoelectric spin currrents (spin Soret currents) and ambipolar coupling with holes. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar diffusion increases the steady-state photo-electron density at the centre and therefore the amplitude of the degeneracy-induced spin-dependent diffusion, while the contribution of the spin Soret current is negligible. Coulomb spin drag and bandgap renormalization are negligible due to electrostatic screening by the hole gas. It is expected for degeneracy to have larger effects in confined systems, such as quantum wells, where both the spin stiffness and the mobility can have a much strong spin dependence.
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effect of the Pauli Principle on photoelectron spin transport in p gaas
Physical Review B, 2015Co-Authors: F Cadiz, D Paget, A C H Rowe, Thierry Amand, P. Barate, Steve ArscottAbstract:In ${p}^{+}$ GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly focused light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about $2\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$ from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli Principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photoelectron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and band-gap renormalization are negligible due to electrostatic screening by the hole gas.
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Effect of the Pauli Principle on photoelectron spin transport in p + GaAs
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2015Co-Authors: F Cadiz, D Paget, Alistair Rowe, Thierry Amand, P. Barate, Steve ArscottAbstract:In p+ GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly focused light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about 2μm from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli Principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photoelectron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and band-gap renormalization are negligible due to electrostatic screening by the hole gas.
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Effect of the Pauli Principle on photoelectron spin transport in $p^+$ GaAs
arXiv: Mesoscale and Nanoscale Physics, 2013Co-Authors: F Cadiz, D Paget, Alistair Rowe, Thierry Amand, P. Barate, Steve ArscottAbstract:In p+ GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly-focussed light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about $2 \; \mu m$ from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli Principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photo-electron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currrents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and bandgap renormalization are negligible due to electrostatic screening by the hole gas.