References of "Schlagheck, Peter"
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See detailNonlinear transport of Bose-Einstein condensates through mesoscopic waveguides
Paul, T.; Hartung, M.; Richter, K. et al

in Physical Review. A (2007), 76(6),

We study the coherent flow of interacting Bose-condensed atoms in mesoscopic waveguide geometries. Analytical and numerical methods, based on the mean-field description of the condensate, are developed to ... [more ▼]

We study the coherent flow of interacting Bose-condensed atoms in mesoscopic waveguide geometries. Analytical and numerical methods, based on the mean-field description of the condensate, are developed to study both stationary as well as time-dependent propagation processes. We apply these methods to the propagation of a condensate through an atomic quantum dot in a waveguide, discuss the nonlinear transmission spectrum and show that resonant transport is generally suppressed due to an interaction-induced bistability phenomenon. Finally, we establish a link between the nonlinear features of the transmission spectrum and the self-consistent quasibound states of the quantum dot. [less ▲]

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See detailEffects of short-range interactions on transport through quantum point contacts: A numerical approach
Lassl, Andreas; Schlagheck, Peter ULg; Richter, Klaus

in Physical Review. B : Condensed Matter (2007), 75(4),

We study electronic transport through a quantum point contact, where the interaction between the electrons is approximated by a contact potential. Our numerical approach is based on the nonequilibrium ... [more ▼]

We study electronic transport through a quantum point contact, where the interaction between the electrons is approximated by a contact potential. Our numerical approach is based on the nonequilibrium Green-function technique which is evaluated at the Hartree-Fock level. We show that this approach allows us to reproduce relevant features of the so-called "0.7 anomaly" observed in the conductance at low temperatures, including the characteristic features in recent shot-noise measurements. This is consistent with a spin-splitting interpretation of the process, and indicates that the 0.7 anomaly should also be observable in transport experiments with ultracold fermionic atoms. [less ▲]

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See detailTunneling in Presence of Chaos and Interactions
Schlagheck, Peter ULg

Thèse d’agrégation de l’enseignement supérieur (2006)

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See detailTunnelling rates for the nonlinear Wannier-Stark problem
Wimberger, S.; Schlagheck, Peter ULg; Mannella, R.

in Journal of Physics : B Atomic Molecular & Optical Physics (2006), 39(3), 729-740

We present a method to numerically compute accurate tunnelling rates for a Bose-Einstein condensate which is described by the nonlinear Gross-Pitaevskii equation. Our method is based on a sophisticated ... [more ▼]

We present a method to numerically compute accurate tunnelling rates for a Bose-Einstein condensate which is described by the nonlinear Gross-Pitaevskii equation. Our method is based on a sophisticated real-time integration of the complex-scaled Gross-Pitaevskii equation, and it is capable of finding the stationary eigenvalues for the Wannier-Stark problem. We show that even weak nonlinearities have significant effects in the vicinity of very sensitive resonant tunnelling peaks, which occur in the rates as a function of the Stark field amplitude. The mean-field interaction induces a broadening and a shift of the peaks, and the latter is explained by an analytic perturbation theory. [less ▲]

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See detailResonance- and Chaos-Assisted Tunneling
Schlagheck, Peter ULg; Eltschka, C.; Ullmo, D.

in Yamanouchi, K.; Chin, S. L.; Agostini, P. (Eds.) et al Progress in Ultrafast Intense Laser Science I (2006)

We consider dynamical tunneling between two symmetry-related regular islands that are separated in phase space by a chaotic sea. Such tunneling processes are dominantly governed by nonlinear resonances ... [more ▼]

We consider dynamical tunneling between two symmetry-related regular islands that are separated in phase space by a chaotic sea. Such tunneling processes are dominantly governed by nonlinear resonances, which induce a coupling mechanism between “regular” quantum states within and “chaotic” states outside the islands. By means of a random matrix ansatz for the chaotic part of the Hamiltonian, one can show that the corresponding coupling matrix element directly determines the level splitting between the symmetric and the antisymmetric eigenstates of the pair of islands. We show in detail how this matrix element can be expressed in terms of elementary classical quantities that are associated with the resonance. The validity of this theory is demonstrated with the kicked Harper model. [less ▲]

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See detailResonance-assisted decay of nondispersive wave packets
Wimberger, Sandro; Schlagheck, Peter ULg; Eltschka, Christopher et al

in Physical Review Letters (2006), 97(4),

We present a quantitative semiclassical theory for the decay of nondispersive electronic wave packets in driven, ionizing Rydberg systems. Statistically robust quantities are extracted combining resonance ... [more ▼]

We present a quantitative semiclassical theory for the decay of nondispersive electronic wave packets in driven, ionizing Rydberg systems. Statistically robust quantities are extracted combining resonance-assisted tunneling with subsequent transport across chaotic phase space and a final ionization step. [less ▲]

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See detailQuantum chaos, transport, and control - In quantum optics
Madronero, Javier; Ponomarev, Alexey; Carvalho, Andre R R et al

in Advances in Atomic and Molecular Physics (2006), 53

Chaos implies unpredictability, fluctuations, and the need for statistical modelling. Quantum optics has developed into one of the most advanced subdisciplines of modern physics in terms of the control of ... [more ▼]

Chaos implies unpredictability, fluctuations, and the need for statistical modelling. Quantum optics has developed into one of the most advanced subdisciplines of modern physics in terms of the control of matter on a microscopic scale, and, in particular, of isolated, single quantum objects. Prima facie, both fields therefore appear rather distant in philosophy and outset. However, as we shall discuss in the present review, chaos, and, more specifically, quantum chaos opens up novel perspectives for our understanding of the dynamics of increasingly complex quantum systems, and of ultimate quantum control by tailoring complexity. [less ▲]

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See detailComplex-scaling approach to the decay of Bose-Einstein condensates
Schlagheck, Peter ULg; Paul, T.

in Physical Review. A (2006), 73(2),

The mean-field dynamics of a Bose-Einstein condensate is studied in the presence of a microscopic trapping potential from which the condensate can escape via tunneling through finite barriers. We show ... [more ▼]

The mean-field dynamics of a Bose-Einstein condensate is studied in the presence of a microscopic trapping potential from which the condensate can escape via tunneling through finite barriers. We show that the method of complex scaling can be used to obtain a quantitative description of this decay process. A real-time propagation approach that is applied to the complex-scaled Gross-Pitaevskii equation allows us to calculate the chemical potentials and lifetimes of the metastably trapped Bose-Einstein condensate. The method is applied to a one-dimensional harmonic confinement potential combined with a Gaussian envelope, for which we compute the lowest symmetric and antisymmetric quasibound states of the condensate. A comparison with alternative approaches using absorbing boundary conditions as well as complex absorbing potentials shows good agreement. [less ▲]

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See detailInfluence of classical resonances on chaotic tunneling
Mouchet, Amaury; Eltschka, Christopher; Schlagheck, Peter ULg

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2006), 74(2),

Dynamical tunneling between symmetry-related stable modes is studied in the periodically driven pendulum. We present strong evidence that the tunneling process is governed by nonlinear resonances that ... [more ▼]

Dynamical tunneling between symmetry-related stable modes is studied in the periodically driven pendulum. We present strong evidence that the tunneling process is governed by nonlinear resonances that manifest within the regular phase-space islands on which the stable modes are localized. By means of a quantitative numerical study of the corresponding Floquet problem, we identify the trace of such resonances not only in the level splittings between near-degenerate quantum states, where they lead to prominent plateau structures, but also in overlap matrix elements of the Floquet eigenstates, which reveal characteristic sequences of avoided crossings in the Floquet spectrum. The semiclassical theory of resonance-assisted tunneling yields good overall agreement with the quantum-tunneling rates, and indicates that partial barriers within the chaos might play a prominent role. [less ▲]

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See detailDecay rates of planar helium
Madronero, J.; Schlagheck, Peter ULg; Hilico, L. et al

in Europhysics Letters [=EPL] (2005), 70(2), 183-189

We compare the autoionization rates of characteristic configurations of the doubly excited helium atom, in one, two and three dimensions. We find that the decay rates of the two-dimensional restriction ... [more ▼]

We compare the autoionization rates of characteristic configurations of the doubly excited helium atom, in one, two and three dimensions. We find that the decay rates of the two-dimensional restriction are in quantitative agreement with those of the real physical system, whilst the one-dimensional model can underestimate the actual decay rates by orders of magnitude. [less ▲]

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See detailNonlinear transport of Bose-Einstein condensates through waveguides with disorder
Paul, T.; Leboeuf, P.; Pavloff, N. et al

in Physical Review. A (2005), 72(6),

We study the coherent flow of a guided Bose-Einstein condensate incident over a disordered region of length L. We introduce a model of disordered potential that originates from magnetic fluctuations ... [more ▼]

We study the coherent flow of a guided Bose-Einstein condensate incident over a disordered region of length L. We introduce a model of disordered potential that originates from magnetic fluctuations inherent to microfabricated guides. This model allows for analytical and numerical studies of realistic transport experiments. The repulsive interaction among the condensate atoms in the beam induces different transport regimes. Below some critical interaction (or for sufficiently small L) a stationary flow is observed. In this regime, the transmission decreases exponentially with increasing L. For strong interaction (or large L), the system displays a transition toward a time-dependent flow with an algebraic decay of the time-averaged transmission. [less ▲]

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See detailResonance- and chaos-assisted tunneling in mixed regular-chaotic systems
Eltschka, C.; Schlagheck, Peter ULg

in Physical Review Letters (2005), 94(1), 014101

We present evidence that nonlinear resonances govern the tunneling process between symmetry-related islands of regular motion in mixed regular-chaotic systems. In a similar way as for near-integrable ... [more ▼]

We present evidence that nonlinear resonances govern the tunneling process between symmetry-related islands of regular motion in mixed regular-chaotic systems. In a similar way as for near-integrable tunneling, such resonances induce couplings between regular states within the islands and states that are supported by the chaotic sea. On the basis of this mechanism, we derive a semiclassical expression for the average tunneling rate, which yields good agreement in comparison with the exact quantum tunneling rates calculated for the kicked rotor and the kicked Harper. [less ▲]

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See detailNonlinear resonant transport of Bose-Einstein condensates
Paul, T.; Richter, K.; Schlagheck, Peter ULg

in Physical Review Letters (2005), 94(2),

The coherent flow of a Bose-Einstein condensate through a quantum dot in a magnetic waveguide is studied. By the numerical integration of the time-dependent Gross-Pitaevskii equation in the presence of a ... [more ▼]

The coherent flow of a Bose-Einstein condensate through a quantum dot in a magnetic waveguide is studied. By the numerical integration of the time-dependent Gross-Pitaevskii equation in the presence of a source term, we simulate the propagation process of the condensate through a double barrier potential in the waveguide. We find that resonant transport is suppressed in interaction-induced regimes of bistability, where multiple scattering states exist at the same chemical potential and the same incident current. We demonstrate, however, that a temporal control of the external potential can be used to circumvent this limitation and to obtain enhanced transmission near the resonance on experimentally realistic time scales. [less ▲]

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See detailNondispersive two-electron wave packets in driven helium
Schlagheck, Peter ULg; Buchleitner, A.

in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2003), 22(3), 401-415

We provide a detailed quantum treatment of the spectral characteristics and of the dynamics of nondispersive two-electron wave packets along the periodically driven, collinear frozen planet configuration ... [more ▼]

We provide a detailed quantum treatment of the spectral characteristics and of the dynamics of nondispersive two-electron wave packets along the periodically driven, collinear frozen planet configuration of helium. These highly correlated, long-lived wave packets arise as a quantum manifestation of regular islands in a mixed classical phase space, which are induced by nonlinear resonances between the external driving and the unperturbed dynamics of the frozen-planet configuration. Particular emphasis is given to the dependence of the ionization rates of the wave packet states on the driving field parameters and on the quantum mechanical phase space resolution, preceded by a comparison of 1D and 3D life times of the unperturbed frozen planet. Furthermore, we study the effect of a superimposed static electric field component, which, on the grounds of classical considerations, is expected to stabilize the real 3D dynamics against large (and possibly ionizing) deviations from collinearity. [less ▲]

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See detailCollinear helium under periodic driving: Stabilization of the asymmetric stretch orbit
Schlagheck, Peter ULg; Pingel, D.; Schmelcher, P.

in Physical Review. A (2003), 68(5), 053410

The collinear eZe configuration of helium, with the electrons on opposite sides of the nucleus, is studied in the presence of an external electromagnetic (laser or microwave) field. We show that the ... [more ▼]

The collinear eZe configuration of helium, with the electrons on opposite sides of the nucleus, is studied in the presence of an external electromagnetic (laser or microwave) field. We show that the classically unstable "asymmetric stretch" orbit, on which doubly excited intrashell states of helium with maximum interelectronic angle are anchored, can be stabilized by means of a resonant driving where the frequency of the electromagnetic field equals the frequency of Kepler-like oscillations along the orbit. A static magnetic field, oriented parallel to the oscillating electric field of the driving, can be used to enforce the stability of the configuration with respect to deviations from collinearity. Quantum Floquet calculations within a collinear model of the driven two-electron atom reveal the existence of nondispersive wave packets localized on the stabilized asymmetric stretch orbit, for double excitations corresponding to principal quantum numbers of the order of Ngreater than or similar to10. [less ▲]

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See detailResonance-assisted tunneling
Brodier, O.; Schlagheck, Peter ULg; Ullmo, D.

in Annals of Physics (2002), 300(1), 88-136

We present evidence that tunneling processes in near-integrable systems are enhanced due to the manifestation of nonlinear resonances and their respective island chains in phase space. A semiclassical ... [more ▼]

We present evidence that tunneling processes in near-integrable systems are enhanced due to the manifestation of nonlinear resonances and their respective island chains in phase space. A semiclassical description of this "resonance-assisted" mechanism is given, which is based on a local perturbative description of the dynamics in the vicinity of the resonances. As an underlying picture, we obtain that the quantum state is coupled, via a succession of classically forbidden transitions across nonlinear resonances, to high excitations within the well, from where tunneling occurs with a rather large rate. The connection between this description and the complex classical structure of the underlying integrable dynamics is furthermore studied, giving ground to the general coherence of the description as well as guidelines for the identification of the dominant tunneling paths. The validity of this mechanism is demonstrated within the kicked Harper model, where good agreement between quantum and semiclassical (resonance-assisted) tunneling rates is found. (C) 2002 Elsevier Science (USA). [less ▲]

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See detailAlgebraic decay of the survival probability in chaotic helium
Schlagheck, Peter ULg; Buchleitner, A.

in Physical Review. A (2001), 63(2), 024701

We demonstrate that the classical helium atom exhibits algebraic decay of the survival probability in the autoionizing eZe configuration. Excitation towards asymptotic orbits of marginal stability is ... [more ▼]

We demonstrate that the classical helium atom exhibits algebraic decay of the survival probability in the autoionizing eZe configuration. Excitation towards asymptotic orbits of marginal stability is identified as the cause of the nonexponential decay. Since one electron travels along a bound Kepler trajectory of infinite excitation in these orbits, we argue that the classical decay law will prevail in the quantum dynamics of a wave packet launched along the eZe configuration. [less ▲]

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See detailResonance-assisted tunneling in near-integrable systems
Brodier, O.; Schlagheck, Peter ULg; Ullmo, D.

in Physical Review Letters (2001), 87(6), 064101

Dynamical tunneling between symmetry related invariant tori is studied in the near-integrable regime. Using the kicked Harper model as an illustration, we show that the exponential decay of the wave ... [more ▼]

Dynamical tunneling between symmetry related invariant tori is studied in the near-integrable regime. Using the kicked Harper model as an illustration, we show that the exponential decay of the wave functions in the classically forbidden region is modified due to coupling processes that are mediated by classical resonances. This mechanism leads to a substantial deviation of the splitting between quasidegenerate eigenvalues from the purely exponential decrease with 1/(h) over bar obtained for the integrable system. A simple semiclassical framework, which takes into account the effect of the resonance substructure on the invariant tori, allows one to quantitatively reproduce the behavior of the eigenvalue splittings. [less ▲]

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See detailLaser-induced transitions between triply excited hollow states
Madsen, L. B.; Schlagheck, Peter ULg; Lambropoulos, P.

in Physical Review. A (2000), 62(6), 062719

Using complex scaling and a correlated basis constructed in terms of B splines, we calculate the Li+ photoion yield in the presence of a laser-induced coupling between the triply excited 2s(2)2p(P-2(0 ... [more ▼]

Using complex scaling and a correlated basis constructed in terms of B splines, we calculate the Li+ photoion yield in the presence of a laser-induced coupling between the triply excited 2s(2)2p(P-2(0)) and 2s2p(2)(D-2(e)) resonances in lithium, the first of which is assumed to be excited by synchrotron radiation from the ground state. The laser coupling between the triply excited states is shown to lead to a significant and readily measurable modification of the line profile which provides a unique probe of the dipole strength between highly correlated triply excited states. We also present results for some higher-lying triply excited states of P-2(0) symmetry. [less ▲]

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See detailLaser-induced transitions between triply excited hollow states
Madsen, L. B.; Schlagheck, Peter ULg; Lambropoulos, P.

in Physical Review Letters (2000), 85(1), 42-45

We present an ab initio calculation of the Li+ photoion yield in the presence of laser coupling between the triply; excited 2s(2)2p(2)P(o) and 2s2p(2) D-2(e) resonances in lithium, the first of which is ... [more ▼]

We present an ab initio calculation of the Li+ photoion yield in the presence of laser coupling between the triply; excited 2s(2)2p(2)P(o) and 2s2p(2) D-2(e) resonances in lithium, the first of which is assumed excited by synchrotron radiation from the ground state. The laser coupling between the triply excited states is shown to lead to a significant and readily measurable modification of the line profile which provides a unique probe of the dipole strength between highly correlated triply excited states. [less ▲]

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