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Vincent Pouthier - One of the best experts on this subject based on the ideXlab platform.
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Vibron phonon coupling strength in a finite size lattice of h bonded peptide units
Physical Review E, 2010Co-Authors: Vincent PouthierAbstract:An attempt is made to measure the Vibron-phonon coupling strength in a finite size lattice of H-bonded peptide units. Within a finite temperature density matrix approach, we compare separately the influence of both the Vibron-phonon coupling and the dipole-dipole interaction on the coherence between the ground state and a local one-Vibron state. Due to the confinement, it is shown that the Vibron-phonon coupling yields a series of dephasing-rephasing mechanisms that prevents the coherence to decay. Similarly, the dipole-dipole interaction gives rise to quantum recurrences for specific revival times. Nevertheless, intense recurrences are rather rare events so that the coherence behaves as a random variable whose most probable value vanishes. By comparing the degree of the coherence for each interaction, a critical coupling chi*(L) is defined to discriminate between the weak and the strong coupling limits. Its size dependence indicates that the smaller the lattice size is, the weaker the Vibron-phonon coupling relative to the dipole-dipole interaction is.
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Vibron phonon in a lattice of h bonded peptide units a criterion to discriminate between the weak and the strong coupling limit
Journal of Chemical Physics, 2010Co-Authors: Vincent PouthierAbstract:Based on dynamical considerations, a simple and intuitive criterion is established to measure the strength of the Vibron-phonon coupling in a lattice of H-bonded peptide units. The main idea is to compare separately the influence of both the Vibron-phonon coupling and the dipole-dipole interaction on a specific element of the Vibron reduced density matrix. This element, which refers to the coherence between the ground state and a local excited amide-I mode, generalizes the concept of survival amplitude at finite temperature. On the one hand, when the dipole-dipole interaction is neglected, it is shown that dephasing-limited coherent dynamics is induced by the Vibron-phonon coupling. On the other hand, when the Vibron-phonon coupling is disregarded, decoherence occurs due to dipole-dipole interactions since the local excited state couples with neighboring local excited states. Therefore, our criterion simply states that the strongest interaction is responsible for the fastest decoherence. It yields a criti...
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Vibron polaron in α helices ii two Vibron bound states
Journal of Chemical Physics, 2005Co-Authors: Cyril Falvo, Vincent PouthierAbstract:The two-Vibron dynamics associated to amide-I vibrations in a three-dimensional (3D) α-helix is described according to a generalized Davydov model. The helix is modeled by three spines of hydrogen-bonded peptide units linked via covalent bonds. It is shown that the two-Vibron energy spectrum supports both a two-Vibron free states continuum and two kinds of bound states, called two-Vibron bound states (TVBS)-I and TVBS-II, connected to the trapping of two Vibrons onto the same amide-I mode and onto two nearest-neighbor amide-I modes belonging to the same spine, respectively. At low temperature, nonvanishing interspine hopping constants yield a three-dimensional nature of both TVBS-I and TVBS-II which the wave functions extend over the three spines of the helix. At biological temperature, the pairs are confined in a given spine and exhibit the same features as the bound states described within a one-dimensional model. The interplay between the temperature and the 3D nature of the helix is also responsible f...
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Vibron polaron in α helices i single Vibron states
Journal of Chemical Physics, 2005Co-Authors: Cyril Falvo, Vincent PouthierAbstract:The Vibron dynamics associated to amide-I vibrations in a three-dimensional alpha-helix is described according to a generalized Davydov model. The helix is modeled by three spines of hydrogen-bonded peptide units linked via covalent bonds. To remove the intramolecular anharmonicity of each amide-I mode and to renormalize the Vibron-phonon coupling, two unitary transformations have been applied to reach the dressed anharmonic Vibron point of view. It is shown that the Vibron dynamics results from the competition between interspine and intraspine Vibron hops and that the two kinds of hopping processes do not experience the same dressing mechanism. Therefore, at low temperature (or weak Vibron-phonon coupling), the polaron behaves as an undressed Vibron delocalized over all the spines whereas at biological temperature (or strong Vibron-phonon coupling), the dressing effect strongly reduces the vibrational exchanges between different spines. As a result the polaron propagates along a single spine as in the one-dimensional Davydov model. Although the helix supports both acoustical and optical phonons, this feature originates in the coupling between the Vibron and the acoustical phonons only. Finally, the lattice distortion which accompanies the polaron has been determined and it is shown that residues located on the excited spine are subjected to a stronger deformation than the other residues.
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localized two Vibron bound state dynamics in a molecular lattice with a defect resonances between bound localized and free states
Physical Review B, 2005Co-Authors: Vincent PouthierAbstract:The two-Vibron dynamics in a molecular nanowire with a local defect is characterized. The integration of the time dependent Schrodinger equation has revealed the occurrence of two singular behaviors. When the defect frequency shift is close to the intramolecular anharmonicity, a resonance between the localized two-Vibron bound state and the two-Vibron free states continuum takes place. The resonance breaks the localized Vibron pair and two independent Vibrons are emitted on each side of the defect so that an exponential decay of the defect vibrational population occurs. By contrast, when the defect frequency shift is almost twice the anharmonicity, a resonance occurs between the localized two-Vibron bound state and the continuum formed by a Vibron trapped on the defect and a second Vibron delocalized along the nanowire. In that case, the trapped Vibron enhances the hopping constant experienced by the second Vibron near the defect so that two localized states occur in which the two Vibrons are trapped around the defect. Due to the superimposition of these two localized states, the vibrational population is strongly localized around the defect and exhibits oscillations similar to that occurring in a classical discrete breather.
Felix Von Oppen - One of the best experts on this subject based on the ideXlab platform.
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electron Vibron coupling in suspended carbon nanotube quantum dots
Physical Review B, 2009Co-Authors: Eros Mariani, Felix Von OppenAbstract:Motivated by recent experiments, we investigate the electron-Vibron coupling in suspended carbon nanotube quantum dots, starting with the electron-phonon coupling of the underlying graphene layer. We show that the coupling strength depends sensitively on the type of Vibron and is strongly sample dependent. The coupling strength becomes particularly strong when inhomogeneity-induced electronic quantum dots are located near regions where the Vibronic mode is associated with large strain. Specifically, we find that the longitudinal stretching mode and the radial breathing mode are coupled via the strong deformation potential, while twist modes couple more weakly via a mechanism involving modulation of the electronic hopping amplitudes between carbon sites. A special case are bending modes: for symmetry reasons, their coupling is only quadratic in the Vibron coordinate. Our results can explain recent experiments on suspended carbon nanotube quantum dots, which exhibit vibrational sidebands accompanied by the Franck-Condon blockade with strong electron-Vibron coupling.
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franck condon blockade in suspended carbon nanotube quantum dots
Nature Physics, 2009Co-Authors: Renaud Leturcq, Christoph Stampfer, K Inderbitzin, Lukas Durrer, Christofer Hierold, Eros Mariani, Maximilian G Schultz, Felix Von Oppen, K EnsslinAbstract:Understanding the influence of vibrational motion of the atoms on electronic transitions in molecules constitutes a cornerstone of quantum physics, as epitomized by the Franck–Condon principle1, 2 of spectroscopy. Recent advances in building molecular-electronics devices3 and nanoelectromechanical systems4 open a new arena for studying the interaction between mechanical and electronic degrees of freedom in transport at the single-molecule level. The tunnelling of electrons through molecules or suspended quantum dots5, 6 has been shown to excite vibrational modes, or Vibrons6, 7, 8, 9. Beyond this effect, theory predicts that strong electron–Vibron coupling strongly suppresses the current flow at low biases, a collective behaviour known as Franck–Condon blockade10, 11. Here, we show measurements on quantum dots formed in suspended single-wall carbon nanotubes revealing a remarkably large electron–Vibron coupling that, owing to the high quality and unprecedented tunability of our samples, allow a quantitative analysis of Vibron-mediated electronic transport in the regime of strong electron–Vibron coupling. This enables us to unambiguously demonstrate the Franck–Condon blockade in a suspended nanostructure. The large observed electron–Vibron coupling could ultimately be a key ingredient for the detection of quantized mechanical motion12, 13. It also emphasizes the unique potential for nanoelectromechanical device applications based on suspended graphene sheets and carbon nanotubes.
Cyril Falvo - One of the best experts on this subject based on the ideXlab platform.
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Vibron polaron in α helices ii two Vibron bound states
Journal of Chemical Physics, 2005Co-Authors: Cyril Falvo, Vincent PouthierAbstract:The two-Vibron dynamics associated to amide-I vibrations in a three-dimensional (3D) α-helix is described according to a generalized Davydov model. The helix is modeled by three spines of hydrogen-bonded peptide units linked via covalent bonds. It is shown that the two-Vibron energy spectrum supports both a two-Vibron free states continuum and two kinds of bound states, called two-Vibron bound states (TVBS)-I and TVBS-II, connected to the trapping of two Vibrons onto the same amide-I mode and onto two nearest-neighbor amide-I modes belonging to the same spine, respectively. At low temperature, nonvanishing interspine hopping constants yield a three-dimensional nature of both TVBS-I and TVBS-II which the wave functions extend over the three spines of the helix. At biological temperature, the pairs are confined in a given spine and exhibit the same features as the bound states described within a one-dimensional model. The interplay between the temperature and the 3D nature of the helix is also responsible f...
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Vibron polaron in α helices i single Vibron states
Journal of Chemical Physics, 2005Co-Authors: Cyril Falvo, Vincent PouthierAbstract:The Vibron dynamics associated to amide-I vibrations in a three-dimensional alpha-helix is described according to a generalized Davydov model. The helix is modeled by three spines of hydrogen-bonded peptide units linked via covalent bonds. To remove the intramolecular anharmonicity of each amide-I mode and to renormalize the Vibron-phonon coupling, two unitary transformations have been applied to reach the dressed anharmonic Vibron point of view. It is shown that the Vibron dynamics results from the competition between interspine and intraspine Vibron hops and that the two kinds of hopping processes do not experience the same dressing mechanism. Therefore, at low temperature (or weak Vibron-phonon coupling), the polaron behaves as an undressed Vibron delocalized over all the spines whereas at biological temperature (or strong Vibron-phonon coupling), the dressing effect strongly reduces the vibrational exchanges between different spines. As a result the polaron propagates along a single spine as in the one-dimensional Davydov model. Although the helix supports both acoustical and optical phonons, this feature originates in the coupling between the Vibron and the acoustical phonons only. Finally, the lattice distortion which accompanies the polaron has been determined and it is shown that residues located on the excited spine are subjected to a stronger deformation than the other residues.
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Vibron-polaron in alpha-helices. II. Two-Vibron bound states
Journal of Chemical Physics, 2005Co-Authors: Cyril Falvo, Vincent PouthierAbstract:The two-Vibron dynamics associated to amide-I vibrations in a 3D alpha-helix is described according to a generalized Davydov model. The helix is modeled by three spines of hydrogen-bonded peptide units linked via covalent bonds. It is shown that the two-Vibron energy spectrum supports both a two-Vibron free states continuum and two kinds of bound states, called TVBS-I and TVBS-II, connected to the trapping of two Vibrons onto the same amide-I mode and onto two nearest neighbor amide-I modes belonging to the same spine, respectively. At low temperature, non vanishing interspine hopping constants yield a three dimensional nature of both TVBS-I and TVBS-II which the wave functions extend over the three spines of the helix. At biological temperature, the pairs are confined in a given spine and exhibit the same features as the bound states described within a one-dimensional model. The interplay between the temperature and the 3D nature of the helix is also responsible for the occurrence of a third bound state called TVBS-III which refers to the trapping of two Vibrons onto two different spines. The experimental signature of the existence of bound states is discussed through the simulation of their infrared pump-probe spectroscopic response. Finally, the fundamental question of the breather-like behavior of two-Vibron bound states is addressed.
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Vibron-polaron in alpha-helices. I. Single-Vibron states
Journal of Chemical Physics, 2005Co-Authors: Cyril Falvo, Vincent PouthierAbstract:The Vibron dynamics associated to amide-I vibrations in a 3D alpha-helix is described according to a generalized Davydov model. The helix is modeled by three spines of hydrogen-bonded peptide units linked via covalent bonds. To remove the intramolecular anharmonicity of each amide-I mode and to renormalized the Vibron-phonon coupling, two unitary transformation have been applied to reach the dressed anharmonic Vibron point of view. It is shown that the Vibron dynamics results from the competition between inter-spine and intra-spine Vibron hops and that the two kinds of hopping processes do not experience the same dressing mechanism. Therefore, at low temperature (or weak Vibron-phonon coupling), the polaron behaves as an undressed Vibron delocalized over all the spines whereas at biological temperature (or strong Vibron-phonon coupling), the dressing effect strongly reduces the vibrational exchanges between different spines. As a result the polaron propagates along a single spine as in the 1D Davydov model. Although the helix supports both acoustical and optical phonons, this feature originates in the coupling between the Vibron and the acoustical phonons, only. Finally, the lattice distortion which accompanies the polaron has been determined and it is shown that residues located on the excited spine are subjected to a stronger deformation than the other residues.
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direct observation of self trapped vibrational states in α helices
Physical Review Letters, 2004Co-Authors: Julian Edler, Vincent Pouthier, Cyril Falvo, Rolf Pfister, Peter HammAbstract:Femtosecond infrared pump-probe spectroscopy of the N-H mode of a stable $\ensuremath{\alpha}$-helix reveals two excited-state absorption bands, which disappear upon unfolding of the helix. A quantitative comparison with polaron theory shows that these two bands reflect two types of two-Vibron bound states connected to the trapping of two Vibrons at the same site and at nearest neighbor sites, respectively. The latter states originate from an acoustic phonon in the helix, which correlates adjacent sites.
Eros Mariani - One of the best experts on this subject based on the ideXlab platform.
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electron Vibron coupling in suspended carbon nanotube quantum dots
Physical Review B, 2009Co-Authors: Eros Mariani, Felix Von OppenAbstract:Motivated by recent experiments, we investigate the electron-Vibron coupling in suspended carbon nanotube quantum dots, starting with the electron-phonon coupling of the underlying graphene layer. We show that the coupling strength depends sensitively on the type of Vibron and is strongly sample dependent. The coupling strength becomes particularly strong when inhomogeneity-induced electronic quantum dots are located near regions where the Vibronic mode is associated with large strain. Specifically, we find that the longitudinal stretching mode and the radial breathing mode are coupled via the strong deformation potential, while twist modes couple more weakly via a mechanism involving modulation of the electronic hopping amplitudes between carbon sites. A special case are bending modes: for symmetry reasons, their coupling is only quadratic in the Vibron coordinate. Our results can explain recent experiments on suspended carbon nanotube quantum dots, which exhibit vibrational sidebands accompanied by the Franck-Condon blockade with strong electron-Vibron coupling.
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franck condon blockade in suspended carbon nanotube quantum dots
Nature Physics, 2009Co-Authors: Renaud Leturcq, Christoph Stampfer, K Inderbitzin, Lukas Durrer, Christofer Hierold, Eros Mariani, Maximilian G Schultz, Felix Von Oppen, K EnsslinAbstract:Understanding the influence of vibrational motion of the atoms on electronic transitions in molecules constitutes a cornerstone of quantum physics, as epitomized by the Franck–Condon principle1, 2 of spectroscopy. Recent advances in building molecular-electronics devices3 and nanoelectromechanical systems4 open a new arena for studying the interaction between mechanical and electronic degrees of freedom in transport at the single-molecule level. The tunnelling of electrons through molecules or suspended quantum dots5, 6 has been shown to excite vibrational modes, or Vibrons6, 7, 8, 9. Beyond this effect, theory predicts that strong electron–Vibron coupling strongly suppresses the current flow at low biases, a collective behaviour known as Franck–Condon blockade10, 11. Here, we show measurements on quantum dots formed in suspended single-wall carbon nanotubes revealing a remarkably large electron–Vibron coupling that, owing to the high quality and unprecedented tunability of our samples, allow a quantitative analysis of Vibron-mediated electronic transport in the regime of strong electron–Vibron coupling. This enables us to unambiguously demonstrate the Franck–Condon blockade in a suspended nanostructure. The large observed electron–Vibron coupling could ultimately be a key ingredient for the detection of quantized mechanical motion12, 13. It also emphasizes the unique potential for nanoelectromechanical device applications based on suspended graphene sheets and carbon nanotubes.
Renaud Leturcq - One of the best experts on this subject based on the ideXlab platform.
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franck condon blockade in suspended carbon nanotube quantum dots
Nature Physics, 2009Co-Authors: Renaud Leturcq, Christoph Stampfer, K Inderbitzin, Lukas Durrer, Christofer Hierold, Eros Mariani, Maximilian G Schultz, Felix Von Oppen, K EnsslinAbstract:Understanding the influence of vibrational motion of the atoms on electronic transitions in molecules constitutes a cornerstone of quantum physics, as epitomized by the Franck–Condon principle1, 2 of spectroscopy. Recent advances in building molecular-electronics devices3 and nanoelectromechanical systems4 open a new arena for studying the interaction between mechanical and electronic degrees of freedom in transport at the single-molecule level. The tunnelling of electrons through molecules or suspended quantum dots5, 6 has been shown to excite vibrational modes, or Vibrons6, 7, 8, 9. Beyond this effect, theory predicts that strong electron–Vibron coupling strongly suppresses the current flow at low biases, a collective behaviour known as Franck–Condon blockade10, 11. Here, we show measurements on quantum dots formed in suspended single-wall carbon nanotubes revealing a remarkably large electron–Vibron coupling that, owing to the high quality and unprecedented tunability of our samples, allow a quantitative analysis of Vibron-mediated electronic transport in the regime of strong electron–Vibron coupling. This enables us to unambiguously demonstrate the Franck–Condon blockade in a suspended nanostructure. The large observed electron–Vibron coupling could ultimately be a key ingredient for the detection of quantized mechanical motion12, 13. It also emphasizes the unique potential for nanoelectromechanical device applications based on suspended graphene sheets and carbon nanotubes.
