Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item Probing localization in absorbing systems via Loschmidt echos.(26/06/2009) Bodyfelt JD; Zheng MC; Kottos T; Kuhl U; Stöckmann H-JWe 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.Item Scaling properties of delay times in one-dimensional random media(3/01/2008) Bodyfelt JD; Méndez-Bermúdez JA; Chabanov A; Kottos TThe 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.Item 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 TA 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.Item Critical Fidelity at the Metal-Insulator Transition(2006) Bodyfelt JD; Ng G; Kottos TUsing 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 statesItem Influence of boundary conditions on quantum escape(1/10/2012) Georgiou O; Gligorić G; Lazarides A; Oliveira DFM; Bodyfelt JD; Goussev AIt 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.Item Coherent and incoherent photon-assisted electron tunneling in optoelectronic molecular devices in soft solids(15/01/2002) Bodyfelt JD; Dahnovsky YAn 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.Item Scaling theory of heat transport in quasi-one-dimensional disordered harmonic chains.(2013-02) Bodyfelt JD; Zheng MC; Fleischmann R; Kottos TWe 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.Item Interactions destroy dynamical localization with strong and weak chaos(EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY, 1/11/2011) Gligorić G; Bodyfelt JD; Flach SBose-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.Item Engineering fidelity echoes in Bose-Hubbard Hamiltonians(1/06/2007) Bodyfelt JD; Hiller M; Kottos TWe 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.Item 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 SWe 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.
