Michel Pleimling

Virginia Polytechnic Institute and State University, Блэксбург, Virginia, United States

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Publications (126)224.88 Total impact

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    ABSTRACT: We discuss the use of Langevin molecular dynamics in the investigation of the non-equilibrium properties of disordered vortex matter. Our special focus is set on values of system parameters that are realistic for disordered high-$T_c$ superconductors such as YBCO. Using a discretized elastic line model, we study different aspects of vortices far from thermal equilibrium. On the one hand we investigate steady-state properties of driven magnetic flux lines in a disordered environment, namely the current-voltage characteristics, the gyration radius, and the pinning time statistics. On the other hand we study the complex relaxation processes and glassy-like dynamics that emerge in type-II superconductors due to the intricate competition between the long-range vortex-vortex repulsion and flux pinning due to randomly placed point defects. To this end we consider different types of sudden perturbations: temperature, magnetic field, and external current quenches.
    Full-text · Article · Sep 2015
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    Michel Pleimling · Uwe C. Tauber
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    ABSTRACT: Vortex lines in type-II superconductors display complicated relaxation processes due to the intricate competition between their mutual repulsive interactions and pinning to attractive point or extended defects. We perform extensive Monte Carlo simulations for an interacting elastic line model with either point-like or columnar pinning centers. From measurements of the space- and time-dependent height-height correlation function for lateral flux line fluctuations, we extract a characteristic correlation length that we use to investigate different non-equilibrium relaxation regimes. The specific time dependence of this correlation length for different disorder configurations displays characteristic features that provide a novel diagnostic tool to distinguish between point-like pinning centers and extended columnar defects.
    Full-text · Article · Jul 2015 · Journal of Statistical Mechanics Theory and Experiment
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    C. Godreche · M. Pleimling
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    ABSTRACT: We investigate the laws of coarsening of a two-dimensional system of Ising spins evolving under single-spin-flip irreversible dynamics at low temperature from a disordered initial condition. The irreversibility of the dynamics comes from the directedness, or asymmetry, of the influence of the neighbours on the flipping spin. We show that the main characteristics of phase ordering at low temperature, such as self-similarity of the patterns formed by the growing domains, and the related scaling laws obeyed by the observables of interest, which hold for reversible dynamics, are still present when the dynamics is directed and irreversible, but with different scaling behaviour. In particular the growth of domains, instead of being diffusive as is the case when dynamics is reversible, becomes ballistic. Likewise, the autocorrelation function and the persistence probability (the probability that a given spin keeps its sign up to time $t$) have still power-law decays but with different exponents.
    Preview · Article · May 2015 · Journal of Statistical Mechanics Theory and Experiment
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    ABSTRACT: We study the effects of rapid temperature and magnetic field changes on the non-equilibrium relaxation dynamics of magnetic vortex lines in disordered type-II superconductors by employing an elastic line model and performing Langevin molecular dynamics simulations. In a previously equilibrated system, either the temperature is suddenly changed, or the magnetic field is instantaneously altered which is reflected in adding or removing flux lines to or from the system. The subsequent aging properties are investigated in samples with either randomly distributed point-like or extended columnar defects, which allows to distinguish the complex relaxation features that result from either type of pinning centers. One-time observables such as the radius of gyration and the fraction of pinned line elements are employed to characterize steady-state properties, and two-time correlation functions such as the vortex line height autocorrelations and their mean-square displacement are analyzed to study the non-linear stochastic relaxation dynamics in the aging regime.
    Full-text · Article · May 2015 · Physical Review E
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    Ben Intoy · Michel Pleimling
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    ABSTRACT: We consider cyclic Lotka-Volterra models with three and four strategies where at every interaction agents play a strategy using a time-dependent probability distribution. Agents learn from a loss by reducing the probability to play a losing strategy at the next interaction. For that, an agent is described as an urn containing $\beta$ balls of three respectively four types where after a loss one of the balls corresponding to the losing strategy is replaced by a ball representing the winning strategy. Using both mean-field rate equations and numerical simulations, we investigate a range of quantities that allow us to characterize the properties of these cyclic models with time-dependent probability distributions. For the three-strategy case in a spatial setting we observe a transition from neutrally stable to stable when changing the level of discretization of the probability distribution. For large values of $\beta$, yielding a good approximation to a continuous distribution, spatially synchronized temporal oscillations dominate the system. For the four-strategy game the system is always neutrally stable, but different regimes emerge, depending on the size of the system and the level of discretization.
    Full-text · Article · Feb 2015 · Physical Review E
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    Mark O. Brown · Robert H. Galyean · Xiangwen Wang · Michel Pleimling
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    ABSTRACT: We discuss relaxation and aging processes in the one- and two-dimensional $ABC$ models. In these driven diffusive systems of three particle types, biased exchanges in one direction yield a coarsening process characterized by a logarithmic growth of ordered domains that take the form of stripes. From the time-dependent length, derived from the equal-time spatial correlator, and from the mean displacement of individual particles different regimes in the formation and growth of these domains can be identified. Analysis of two-times correlation and response functions reveals dynamical scaling in the asymptotic logarithmic growth regime as well as complicated finite-time and finite-size effects in the early and intermediate time regimes.
    Preview · Article · Feb 2015 · Physical Review E
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    Nicholas Borchers · Michel Pleimling · R. K. P. Zia
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    ABSTRACT: The statistical mechanics of a one-dimensional Ising model in thermal equilibrium is well-established, textbook material. Yet, when driven far from equilibrium by coupling two sectors to two baths at different temperatures, it exhibits remarkable phenomena, including an unexpected 'freezing by heating.' These phenomena are explored through systematic numerical simulations. Our study reveals complicated relaxation processes as well as a crossover between two very different steady-state regimes.
    Preview · Article · Nov 2014 · Physical Review E
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    James Mayberry · Keith Tauscher · Michel Pleimling
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    ABSTRACT: Synthetic antiferromagnets with strong perpendicular anisotropy can be modeled by layered Ising antiferromagnets. Accounting for the fact that in the experimental systems the ferromagnetic layers, coupled antiferromagnetically via spacers, are multilayers, we propose a description through Ising films where ferromagnetic stacks composed of multiple layers are coupled antiferromagnetically. We study the equilibrium and non-equilibrium properties of these systems where we vary the number of layers in each stack. Using numerical simulations, we construct equilibrium temperature$-$magnetic field phase diagrams for a variety of cases. We find the same dominant features (three stable phases, where one phase boundary ends in a critical end point, whereas the other phase boundary shows a tricritical point at which the transition changes from first to second order) for all studied cases. Using time-dependent quantities, we also study the ordering processes that take place after a temperature quench. The nature of long-lived metastable states are discussed for thin films, whereas for thick films we compute the surface autocorrelation exponent.
    Preview · Article · Jul 2014 · Physical Review B
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    Ulrich Dobramysl · Michel Pleimling · Uwe C. Tauber
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    ABSTRACT: We study the pinning dynamics of magnetic flux (vortex) lines in a disordered type-II superconductor. Using numerical simulations of a directed elastic line model, we extract the pinning time distributions of vortex line segments. We compare different model implementations for the disorder in the surrounding medium: discrete, localized pinning potential wells that are either attractive and repulsive or purely attractive, and whose strengths are drawn from a Gaussian distribution; as well as continuous Gaussian random potential landscapes. We find that both schemes yield power law distributions in the pinned phase as predicted by extreme-event statistics, yet they differ significantly in their effective scaling exponents and their short-time behavior.
    Full-text · Article · May 2014 · Physical Review E
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    Matthew T. Shimer · Uwe C. Tauber · Michel Pleimling
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    ABSTRACT: We employ Monte Carlo simulations to investigate the non-equilibrium relaxation properties of the two- and three-dimensional Coulomb glass with different long-range repulsive interactions. Specifically, we explore the aging scaling laws in the two-time density autocorrelation function. We find that in the time window and parameter range accessible to us, the scaling exponents are not universal, depending on the filling fraction and temperature: As either the temperature decreases or the filling fraction deviates more from half-filling, the exponents reflect markedly slower relaxation kinetics. In comparison with a repulsive Coulomb potential, appropriate for impurity states in strongly disordered semiconductors, we observe that for logarithmic interactions, the soft pseudo-gap in the density of states is considerably broader, and the dependence of the scaling exponents on external parameters is much weaker. The latter situation is relevant for flux creep in the disorder-dominated Bose glass phase of type-II superconductors subject to columnar pinning centers.
    Full-text · Article · Mar 2014 · Physical Review E
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    Shahir Mowlaei · Ahmed Roman · Michel Pleimling
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    ABSTRACT: In order to model real ecological systems one has to consider many species that interact in complex ways. However, most of the recent theoretical studies have been restricted to few species systems with rather trivial interactions. The few studies dealing with larger number of species and/or more complex interaction schemes are mostly restricted to numerical explorations. In this paper we determine, starting from the deterministic mean-field rate equations, for large classes of systems the space of coexistence fixed points at which biodiversity is maximal. For systems with a single coexistence fixed point we derive complex Ginzburg-Landau equations that allow to describe space-time pattern realized in two space dimensions. For selected cases we compare the theoretical predictions with the pattern observed in numerical simulations.
    Full-text · Article · Mar 2014 · Journal of Physics A Mathematical and Theoretical
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    Keith Tauscher · Michel Pleimling
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    ABSTRACT: We study the surface phase diagram of the three-dimensional kinetic Ising model below the equilibrium critical point subjected to a periodically oscillating magnetic field. Changing the surface interaction strength as well as the period of the external field, we obtain a non-equilibrium surface phase diagram that in parts strongly resembles the corresponding equilibrium phase diagram, with an ordinary transition, an extraordinary transition and a surface transition. These three lines meet at a special transition point. For weak surface couplings, however, the surface does not order. These results are found to remain qualitatively unchanged when using different single-spin flip dynamics.
    Preview · Article · Feb 2014 · Physical Review E
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    Claude Godreche · Michel Pleimling
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    ABSTRACT: We consider the non-conserved dynamics of the Ising model on the two-dimensional square lattice, where each spin is influenced preferentially by its East and North neighbours. The single-spin flip rates are such that the stationary state is Gibbsian with respect to the usual ferromagnetic Ising Hamiltonian. We show the existence, in the paramagnetic phase, of a dynamical transition between two regimes of violation of the fluctuation-dissipation theorem in the nonequilibrium stationary state: a regime of weak violation where the stationary fluctuation-dissipation ratio is finite, when the asymmetry parameter is less than a threshold value, and a regime of strong violation where this ratio vanishes asymptotically above the threshold. The present study suggests that this novel kind of dynamical transition in nonequilibrium stationary states, already found for the directed Ising chain and the spherical model with asymmetric dynamics, might be quite general. In contrast with the later models, the equal-time correlation function for the two-dimensional directed Ising model depends on the asymmetry.
    Full-text · Article · Jan 2014 · Journal of Statistical Mechanics Theory and Experiment
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    Linjun Li · Michel Pleimling
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    ABSTRACT: Systems with a bulk first-order transition can display diverging correlation lengths close to a surface. This surface induced disordering yields a special type of surface criticality. Using extensive numerical simulations we study surface quantities in the two-dimensional Potts model with a large number of states $q$ which undergoes a discontinuous bulk transition. The surface critical exponents are thereby found to depend on the value of $q$, which is in contrast to prior claims that these exponents should be universal and independent of $q$. It follows that surface induced disordering at first-order transitions is characterized by exponents that depend on the details of the model.
    Preview · Article · Nov 2013 · Physical Review B
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    Ben Intoy · Michel Pleimling
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    ABSTRACT: When four species compete stochastically in a cyclic way, the formation of two teams of mutually neutral partners is observed. In this paper we study through numerical simulations the extinction processes that can take place in this system both in the well mixed case as well as on different types of lattices. The different routes to extinction are revealed by the probability distribution of the domination time, i.e. the time needed for one team to fully occupy the system. If swapping is allowed between neutral partners, then the probability distribution is dominated by very long-lived states where a few very large domains persist, each domain being occupied by a mix of individuals from species that form one of the teams. Many aspects of the possible extinction scenarios are lost when only considering averaged quantities as for example the mean domination time.
    Full-text · Article · Jul 2013 · Journal of Statistical Mechanics Theory and Experiment
  • Hyunhang Park · Michel Pleimling

    No preview · Article · Jun 2013 · Physical Review Letters
  • Ahmed Roman · Debanjan Dasgupta · Michel Pleimling
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    ABSTRACT: In order to better understand the interplay of partnership and competition in population dynamics, we study a family of generalized May-Leonard models with N species. These models have a very rich structure, characterized by different types of space-time patterns. Interesting partnership formations emerge following the maxim that “the enemy of my enemy is my friend”. In specific cases cyclic dominance within coarsening clusters yields a peculiar coarsening behavior with intriguing pattern formation. We classify the different types of dynamics through the analysis of the square of the adjacency matrix. The dependence of the population densities on emerging pattern and propagating wave fronts is elucidated through a Fourier analysis. Finally, after having identified collaborating teams, we study interface fluctuations where we initially populate different parts of the system with different teams.
    No preview · Article · Mar 2013 · Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics
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    Hyunhang Park · Michel Pleimling
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    ABSTRACT: Using numerical simulations we investigate the properties of the dynamic phase transition that is encountered in the three-dimensional Ising model subjected to a periodically oscillating magnetic field. The values of the critical exponents are determined through finite-size scaling. Our results show that the studied non-equilibrium phase transition belongs to the universality class of the equilibrium three-dimensional Ising model.
    Preview · Article · Mar 2013 · Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics
  • Linjun Li · Michel Pleimling
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    ABSTRACT: Using extensive Monte Carlo simulations we study the properties of the non-equilibrium phase transition encountered in driven three-dimensional Potts systems with magnetic friction. Our system consists of two three-dimensional blocks, coupled through boundary spins, that move along their boundaries with a constant relative velocity. Changing the number of states in the system from two (Ising case) to nine states, we find different scenarios for the surface behavior depending on whether the bulk transition is continuous or discontinuous. In order to fully assess the properties of this non-equilibrium phase transition, we vary systematically the strength of the coupling between the two blocks as well as the value of the relative velocity. For strong couplings between the blocks the phase transition is found to be strongly anisotropic.
    No preview · Article · Mar 2013
  • Nick Borchers · Michel Pleimling · R. K. P. Zia
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    ABSTRACT: From complex biological systems to a simple simmering pot, thermodynamic systems held out of equilibrium are exceedingly common in nature. Despite this, a general theory to describe these types of phenomena remains elusive. In this talk, we explore a simple modification of the venerable Ising model in hopes of shedding some light on these issues. In both one and two dimensions, systems attached to two distinct heat reservoirs exhibit many of the hallmarks of phase transition. When such systems settle into a non-equilibrium steady-state they exhibit numerous interesting phenomena, including an unexpected ``freezing by heating.'' There are striking and surprising similarities between the behavior of these systems in one and two dimensions, but also intriguing differences. These phenomena will be explored and possible approaches to understanding the behavior will be suggested.
    No preview · Article · Mar 2013

Publication Stats

1k Citations
224.88 Total Impact Points

Institutions

  • 2007-2015
    • Virginia Polytechnic Institute and State University
      • Department of Physics
      Блэксбург, Virginia, United States
  • 2014
    • University of Oxford
      Oxford, England, United Kingdom
  • 2000-2007
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      • Institute of Theoretical Physics
      Erlangen, Bavaria, Germany
  • 2006
    • University of Florence
      Florens, Tuscany, Italy
  • 1997-1998
    • RWTH Aachen University
      • Institut für Theorie der statistischen Physik A
      Aachen, North Rhine-Westphalia, Germany
    • Universität des Saarlandes
      • Physikalische und Theoretische Chemie
      Saarbrücken, Saarland, Germany