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 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 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.Item Detangling flat bands into Fano lattices(EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY, 1/02/2014) Flach S; Leykam D; Bodyfelt JD; Matthies P; Desyatnikov ASMacroscopically 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.Item 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 SWe 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.
