Browsing by Author "Bodyfelt JD"

Now showing 1 - 17 of 17
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    Coherent and incoherent photon-assisted electron tunneling in optoelectronic molecular devices in soft solids
    (15/01/2002) Bodyfelt JD; Dahnovsky Y
    An electron in a bath with slow degrees of freedom (such as soft solids, e.g., proteins) is driven by a strong time-dependent electric field. In this molecular device, the electron dynamics are characterized by quasicoherent oscillations with slow square-root decay even at room temperatures. The frequency of the oscillations and the equilibrium distribution are found essentially to depend on the field intensity and the medium parameters. The applied field effectively changes the relaxation time of the environment from fast to slow and vice versa. The quasicoherence allows for the prevention of overheating in the microdevice. It is also shown that the applied field is capable of changing the character of the electron dynamics from quasicoherence to incoherent decay. The electron transition probability strongly depends upon the applied voltage (bias) and at some values of the field parameters, this voltage can quickly switch the coherent transfer over to incoherent transfer and vice versa. Despite the slow electron transfer in the incoherence region, the equilibrium distribution can favor either products or reactants, depending upon the field intensity. In the incoherent regime, the electron localization is possible. All these features can be exploited in microcomputers or quantum computers.
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    Critical Fidelity at the Metal-Insulator Transition
    (2006) Bodyfelt JD; Ng G; Kottos T
    Using a Wigner Lorentzian random matrix ensemble, we study the fidelity, F(t), of systems at the Anderson metal-insulator transition, subject to small perturbations that preserve the criticality. We find that there are three decay regimes as perturbation strength increases: the first two are associated with a Gaussian and an exponential decay, respectively, and can be described using linear response theory. For stronger perturbations F(t) decays algebraically as F(t)∼t-D2μ, where D2μ is the correlation dimension of the local density of states
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    Detangling flat bands into Fano lattices
    (EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY, 1/02/2014) Flach S; Leykam D; Bodyfelt JD; Matthies P; Desyatnikov AS
    Macroscopically degenerate flat bands (FB) in periodic lattices host compact localized states which appear due to destructive interference and local symmetry. Interference provides a deep connection between the existence of flat band states (FBS) and the appearance of Fano resonances for wave propagation. We introduce generic transformations detangling FBS and dispersive states into lattices of Fano defects. Inverting the transformation, we generate a continuum of FB models. Our procedure allows us to systematically treat perturbations such as disorder and explain the emergence of energy-dependent localization length scaling in terms of Fano resonances. © Copyright EPLA, 2014.
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    Engineering fidelity echoes in Bose-Hubbard Hamiltonians
    (1/06/2007) Bodyfelt JD; Hiller M; Kottos T
    We analyze the fidelity decay for a system of interacting bosons described by a Bose-Hubbard Hamiltonian. We find echoes associated with "non-universal" structures that dominate the energy landscape of the perturbation operator. Despite their classical origin, these echoes persist deep into the quantum (perturbative) regime and can be described by an improved random matrix modeling. In the opposite limit of strong perturbations (and high enough energies), classical considerations reveal the importance of self-trapping phenomena in the echo efficiency. © Europhysics Letters Association.
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    Erratum: Detangling flat bands into Fano lattices
    (EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY, 1/01/2014) Flach S; Leykam D; Bodyfelt JD; Matthies P; Desyatnikov AS
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    Flatbands under correlated perturbations.
    (AMER PHYSICAL SOC, 5/12/2014) Bodyfelt JD; Leykam D; Danieli C; Yu X; Flach S
    Flatband networks are characterized by the coexistence of dispersive and flatbands. Flatbands (FBs) are generated by compact localized eigenstates (CLSs) with local network symmetries, based on destructive interference. Correlated disorder and quasiperiodic potentials hybridize CLSs without additional renormalization, yet with surprising consequences: (i) states are expelled from the FB energy E_{FB}, (ii) the localization length of eigenstates vanishes as ξ∼1/ln(E-E_{FB}), (iii) the density of states diverges logarithmically (particle-hole symmetry) and algebraically (no particle-hole symmetry), and (iv) mobility edge curves show algebraic singularities at E_{FB}. Our analytical results are based on perturbative expansions of the CLSs and supported by numerical data in one and two lattice dimensions.
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    Influence of boundary conditions on quantum escape
    (1/10/2012) Georgiou O; Gligorić G; Lazarides A; Oliveira DFM; Bodyfelt JD; Goussev A
    It has recently been established that quantum statistics can play a crucial role in quantum escape. Here we demonstrate that boundary conditions can be equally important - moreover, in certain cases, may lead to a complete suppression of the escape. Our results are exact and hold for arbitrarily many particles. © Copyright EPLA, 2012.
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    Interactions Destroy Dynamical Localization with Strong & Weak Chaos
    (1/11/2011) Bodyfelt JD; Flach S; Gligoric G
    Bose-Einstein condensates loaded into kicked optical lattices can be treated as quantum kicked-rotor systems. Noninteracting rotors show dynamical localization in momentum space. The experimentally tunable condensate interaction is included in a qualitative Gross-Pitaevskii-type model based on two-body interactions. We observe strong- and weak-chaos regimes of wave packet spreading in momentum space. In the intermediate strong-chaos regime the condensate energy grows as t1/2. In the asymptotic weak-chaos case the growth crosses over into a t1/3 law. The results do not depend on the details of the kicking. © Europhysics Letters Association.
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    Interactions destroy dynamical localization with strong and weak chaos
    (EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY, 1/11/2011) Gligorić G; Bodyfelt JD; Flach S
    Bose-Einstein condensates loaded into kicked optical lattices can be treated as quantum kicked-rotor systems. Noninteracting rotors show dynamical localization in momentum space. The experimentally tunable condensate interaction is included in a qualitative Gross-Pitaevskii-type model based on two-body interactions. We observe strong- and weak-chaos regimes of wave packet spreading in momentum space. In the intermediate strong-chaos regime the condensate energy grows as t1/2. In the asymptotic weak-chaos case the growth crosses over into a t1/3 law. The results do not depend on the details of the kicking. © Europhysics Letters Association.
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    Nonlinear waves in disordered chains: probing the limits of chaos and spreading.
    (AMER PHYSICAL SOC, 2011-07) Bodyfelt JD; Laptyeva TV; Skokos C; Krimer DO; Flach S
    We probe the limits of nonlinear wave spreading in disordered chains which are known to localize linear waves. We particularly extend recent studies on the regimes of strong and weak chaos during subdiffusive spreading of wave packets [Europhys. Lett. 91, 30001 (2010)] and consider strong disorder, which favors Anderson localization. We probe the limit of infinite disorder strength and study Fröhlich-Spencer-Wayne models. We find that the assumption of chaotic wave packet dynamics and its impact on spreading is in accord with all studied cases. Spreading appears to be asymptotic, without any observable slowing down. We also consider chains with spatially inhomogeneous nonlinearity, which give further support to our findings and conclusions.
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    Observation of asymmetric transport in structures with active nonlinearities.
    (7/06/2013) Bender N; Factor S; Bodyfelt JD; Ramezani H; Christodoulides DN; Ellis FM; Kottos T
    A mechanism for asymmetric transport which is based on parity-time-symmetric nonlinearities is presented. We show that in contrast to the case of conservative nonlinearities, an increase of the complementary conductance strength leads to a simultaneous increase of asymmetry and transmittance intensity. We experimentally demonstrate the phenomenon using a pair of coupled Van der Pol oscillators as a reference system, each with complementary anharmonic gain and loss conductances, connected to transmission lines. An equivalent optical setup is also proposed.
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    Probing localization in absorbing systems via Loschmidt echos.
    (26/06/2009) Bodyfelt JD; Zheng MC; Kottos T; Kuhl U; Stöckmann H-J
    We measure Anderson localization in quasi-one-dimensional waveguides in the presence of absorption by analyzing the echo dynamics due to small perturbations. We specifically show that the inverse participation number of localized modes dictates the decay of the Loschmidt echo, differing from the Gaussian decay expected for diffusive or chaotic systems. Our theory, based on a random matrix modeling, agrees perfectly with scattering echo measurements on a quasi-one-dimensional microwave cavity filled with randomly distributed scatterers.
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    Scaling properties of delay times in one-dimensional random media
    (3/01/2008) Bodyfelt JD; Méndez-Bermúdez JA; Chabanov A; Kottos T
    The scaling properties of the inverse moments of Wigner delay times are investigated in finite one-dimensional (1D) random media with one channel attached to the boundary of the sample. We find that they follow a simple scaling law which is independent of the microscopic details of the random potential. Our theoretical considerations are confirmed numerically for systems as diverse as 1D disordered wires and optical lattices to microwave waveguides with correlated scatterers. © 2008 The American Physical Society.
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    Scaling theory of heat transport in quasi-one-dimensional disordered harmonic chains.
    (2013-02) Bodyfelt JD; Zheng MC; Fleischmann R; Kottos T
    We introduce a variant of the banded random matrix ensemble and show, using detailed numerical analysis and theoretical arguments, that the phonon heat current in disordered quasi-one-dimensional lattices obeys a one-parameter scaling law. The resulting β function indicates that an anomalous Fourier law is applicable in the diffusive regime, while in the localization regime the heat current decays exponentially with the sample size. Our approach opens a new way to investigate the effects of Anderson localization in heat conduction based on the powerful ideas of scaling theory.
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    Subdiffusion of nonlinear waves in quasiperiodic potentials
    (IOP PUBLISHING LTD, 1/10/2012) Larcher M; Laptyeva TV; Bodyfelt JD; Dalfovo F; Modugno M; Flach S
    We study the time evolution of wave packets in one-dimensional quasiperiodic lattices which localize linear waves. Nonlinearity (related to two-body interactions) has a destructive effect on localization, as observed recently for interacting atomic condensates (Lucioni et al 2011 Phys. Rev. Lett. 106 230403). We extend the analysis of the characteristics of the subdiffusive dynamics to large temporal and spatial scales. Our results for the second moment m 2 consistently reveal an asymptotic m 2 ∼ t 1/3 and an intermediate m 2 ∼ t 1/2 law. At variance with purely random systems (Laptyeva et al 2010 Europhys. Lett. 91 30001), the fractal gap structure of the linear wave spectrum strongly favours intermediate self-trapping events. Our findings give a new dimension to the theory of wave packet spreading in localizing environments. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
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    Subdiffusion of nonlinear waves in two-dimensional disordered lattices
    (EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY, 1/06/2012) Laptyeva TV; Bodyfelt JD; Flach S
    We perform high-precision computational experiments on nonlinear waves in two-dimensional disordered lattices with tunable nonlinearity. While linear wave packets are trapped due to Anderson localization, nonlinear wave packets spread subdiffusively. Various speculations on the growth of the second moment as t α are tested. Using fine statistical averaging we find agreement with predictions from Flach S., Chem. Phys., 375 (2010) 548, which supports the concepts of strong and weak chaos for nonlinear wave propagation in disordered media. We extend our approach and find potentially long-lasting intermediate deviations due to a growing number of surface resonances of the wave packet. © 2012 EPLA.
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    The crossover from strong to weak chaos for nonlinear waves in disordered systems
    (EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY, 1/08/2010) Laptyeva TV; Bodyfelt JD; Krimer DO; Skokos C; Flach S
    We observe a crossover from strong to weak chaos in the spatiotemporal evolution of multiple-site excitations within disordered chains with cubic nonlinearity. Recent studies have shown that Anderson localization is destroyed, and the wave packet spreading is characterized by an asymptotic divergence of the second moment m2 in time (as t1/3), due to weak chaos. In the present paper, we observe the existence of a qualitatively new dynamical regime of strong chaos, in which the second moment spreads even faster (as t1/2), with a crossover to the asymptotic law of weak chaos at larger times. We analyze the pecularities of these spreading regimes and perform extensive numerical simulations over large times with ensemble averaging. A technique of local derivatives on logarithmic scales is developed in order to quantitatively visualize the slow crossover processes. Copyright © 2010 EPLA.