Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session L3: Topics in Statistical Physics II |
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Sponsoring Units: GSNP Chair: Marco Mazza, Max Planck Institute for Dynamics and Self-Organization Room: 002AB |
Wednesday, March 4, 2015 8:00AM - 8:12AM |
L3.00001: Concept of Linear Thermal Circulator Based on Coriolis forces Huanan Li, Tsampikos Kottos Directional transport and the creation of non-reciprocal devices that control the flow of energy and/or mass at predefined directions have been posing always fascinating challenges. In this contribution, we show that the presence of a Coriolis force in a rotating linear lattice imposes a non-reciprocal propagation of the phononic heat carriers. Using this effect we propose the concept of Coriolis linear thermal circulator which can control the circulation of a heat current. A simple model of three coupled harmonic masses on a rotating platform allow us to demonstrate giant circulating rectification effects for moderate values of the angular velocities of the platform. [Preview Abstract] |
Wednesday, March 4, 2015 8:12AM - 8:24AM |
L3.00002: Magnetically driven quantum heat engine Enrique Munoz, Francisco Pena In analogy with classical thermodynamics, a quantum heat engine generates useful mechanical work from heat, by means of a reversible sequence of transformations (trajectories), where the ``working substance'' is of quantum mechanical nature. Several theoretical implementations for a quantum heat engine have been discussed in the literature, such as entangled states in a qubit, quantum mechanical versions of the Otto cycle, and photocells. In this work [1], we propose yet a different alternative by introducing the concept of a magnetically driven quantum heat engine. We studied the efficiency of such system, by considering as the ``working substance'' a single nonrelativistic particle trapped in a cylindrical potential well, as a model for a semiconductor quantum dot, in the presence of an external magnetic field. The trajectories are driven by a quasistatic modulation of the external magnetic-field intensity, while the system is in contact with macroscopic thermostats. The external magnetic field modulation allows to modify the effective geometric confinement, in analogy with a piston in a classical gas.\\[4pt] [1] E. Munoz and F. J. Pena, Physical Review E 89, 052107 (2014). [Preview Abstract] |
Wednesday, March 4, 2015 8:24AM - 8:36AM |
L3.00003: ABSTRACT WITHDRAWN |
Wednesday, March 4, 2015 8:36AM - 8:48AM |
L3.00004: Why are all dualities conformal? Theory and practical consequences Seyyed Mohammad Sadegh Vaezi, Zoharn Nussinov, Gerardo Ortiz We relate duality mappings to the ``Babbage equation'' F(F(z)) = z with F a map linking weak to strong coupling theories. Under fairly general conditions F may only be a specific conformal transformation of the fractional linear type. This deep general result has enormous practical consequences. For example, one can establish that weak and strong coupling expansions are trivially related, i.e., one needs to generate only one of them while the other is automatically determined through a set of linear constraints. The latter partially solve or, equivalently, localize the computational complexity to a simple fraction of the coefficients, and as a bonus those relations encode non-trivial equalities between different geometric constructions. We illustrate our findings by examining various models including, but not limited to, ferromagnetic and spin-glass type Ising models on hypercubic lattices. [Preview Abstract] |
Wednesday, March 4, 2015 8:48AM - 9:00AM |
L3.00005: ABSTRACT WITHDRAWN |
Wednesday, March 4, 2015 9:00AM - 9:12AM |
L3.00006: Quantifying the Effects of Noise on Diffuse Interface Models: Cahn-Hilliard-Cook equations Spencer Pfeifer, Baskar Ganapathysubramanian We present an investigation into the dynamics of phase separation through numerical simulations of the Cahn-Hilliard-Cook (CHC) equation. This model is an extension of the well-known Cahn- Hilliard equation, perturbed by an additive white noise. Studies have shown that random fluctuations are critical for proper resolution of physical phenomena. This is especially true for phase critical systems. We explore the transient behavior of the solution space for varying levels of noise. This is enabled by our massively scalable finite element-based numerical framework. We briefly examine the interplay between noise level and discretization (spatial and temporal) in obtaining statistically consistent solutions. We show that the added noise accelerates progress towards phase separation, but retards dynamics throughout subsequent coarsening. We identify a scaling exponent relating morphology metrics with the level of noise. We observe a very clear scaling effect of finite domain size, which is observed to be offset by increasing levels of noise. Domain scaling reveals a clear microstructural asymmetry at various stages of the evolution for lower noise levels. In contrast, higher noise levels tend to produce more uniform morphologies. [Preview Abstract] |
Wednesday, March 4, 2015 9:12AM - 9:24AM |
L3.00007: Definitions of temperature in non-extensive systems Sergio Davis, Gonzalo Guti\'errez Superstatistics (Beck and Cohen, 2003) is a proposed formalism for explaining the presence of non-Boltzmann distributions in Nature for systems out of equilibrium. The superstatistical ensemble is a superposition of canonical ensembles according to \begin{equation} P(\vec r, \vec p|H) = \int_0^\infty d\beta P(\beta|H)\frac{\exp(-\beta \mathcal{H}(\vec r, \vec p))}{Z(\beta)}, \end{equation} with $P(\beta|H)$ the probability density for the inverse temperature parameter $\beta$. In this work we show that, in order for this formalism to be internally consistent, it is impossible to have a definition of $\beta$ as an observable which is valid across all ``superstatistical'' ensembles. In other words, the shape of the ensemble cannot be determined by measuring temperature, only by measuring energy. Our results also reveal the fact that energy and temperature are not in the same footing as observables for non-canonical ensembles. [Preview Abstract] |
Wednesday, March 4, 2015 9:24AM - 9:36AM |
L3.00008: Non-reciprocal acoustic transport in media with spectral asymmetry and losses Andrea Kleeman, Rahul Deora, Huanan Li, Fred Ellis, Tsampikos Kottos, Ilya Vitebskiy We propose a novel scheme for acoustic isolators, which rely on the interplay of spectral asymmetry and distributed losses. The spectral asymmetry is imposed to the system via a flow, which is moving inside a corrugated waveguide with a constant velocity. A result of this spectra asymmetry is that left and right moving acoustic waves have different group velocities. Then, depending on the direction of the incident acoustic signal, inherent losses result in different level of attenuation of the transmitted signal. The outgoing acoustic wave has the same frequency characteristics as the incoming one. An experimental realization of our proposal is also discussed. [Preview Abstract] |
Wednesday, March 4, 2015 9:36AM - 9:48AM |
L3.00009: Density reconstruction via maximum entropy method Austin McDonald, Raymond Atta-Fynn, Parthapratim Biswas We demonstrate an application of the maximum entropy principle by employing the Shannon entropy functional to reconstruct functions that are otherwise non-trivial to reproduce by existing reconstruction techniques. Specifically, we present the reconstruction of the Dirac comb by maximizing the Shannon entropy subject to the moment constraints using Monte-Carlo type and population-based approaches. The results are compared with the existing results in the literature and the convergence properties of the resulting distributions are examined in relation to the number of input moments. [Preview Abstract] |
Wednesday, March 4, 2015 9:48AM - 10:00AM |
L3.00010: Density of Yang-Lee zeros in the thermodynamic limit using Tensor RG Artur Garcia-Saez, Tzu-Chieh Wei The partition function of ferromagnets in a lattice is represented as a Tensor Network and efficiently contracted using an iterative RG process. The density of Yang-Lee zeros on the complex field plane is obtained from accurate calculations of the free energy and local observables in an effective thermodynamic limit. We illustrate this approach studying the distribution of Yang-Lee zeros for the Ising model in 2D and 3D square lattices. [Preview Abstract] |
Wednesday, March 4, 2015 10:00AM - 10:12AM |
L3.00011: Entanglement Thermalization and Local Conservation Laws Liangsheng Zhang, Hyungwon Kim, David Huse We study the thermalization of entanglement entropy in one-dimensional spin chains under the unitary dynamics of a nonintegrable Hamiltonian or periodic driving by Floquet operators. Using full diagonalization of the Hamiltonian matrix and the Floquet operators, we analyze the time evolution of entanglement entropy starting from various initial conditions, including initial states with entanglement in excess of the thermal equilibrium value. It is found that the thermalization of entanglement entropy is coupled to local conservation laws when approaching equilibrium, and the absence of conservation laws in the Floquet system allows the entanglement entropy to thermalize more rapidly than it does in the corresponding Hamiltonian. [Preview Abstract] |
Wednesday, March 4, 2015 10:12AM - 10:24AM |
L3.00012: Phase transitions in a confined monolayer of magnetized beads Julien Schockmel We present experimental results obtained with a model experimental system dedicated to the study of 2D phase transitions. The system is composed of millimetric beads interacting through magnetic dipole-dipole interaction. Due to the confinement, repulsive interactions tends to order the system. In addition, the system is submitted to a controlled mechanical agitation which produce an erratic motion of the beads and thus creates disorder. Controlling the competition between interaction energy and entropy, allows us to explore different structures of 2 dimensional systems. At first, the melting of a two dimensional crystal is studied. As predicted by the KTHNY theory, a two stage melting is observed, including the so-called hexatic phase (see results in Phys. Rev. E.87, 062201 (2013)). Afterward, the behavior of binary systems is studied. In particular, the effect of the grains polydispersity on the order is analyzed. [Preview Abstract] |
Wednesday, March 4, 2015 10:24AM - 10:36AM |
L3.00013: Complex Pole Approach in Thermodynamic Description of Fluid Mixtures with Small Number of Molecules Timur Aslyamov, Oleg Dinariev Physically consistent description of equilibrium small molecular systems requires the extension of thermodynamics. The reason is the absence of thermodynamic limit, which is mandatory for the applicability of classical thermodynamics. New theoretical method of complex pole decomposition for the statistical description of small multicomponent molecular systems is implemented. Similar approach has been previously developed and applied in nuclear physics for finite systems of nucleons. We have significantly transformed and extended the original formulation to make it work for multicomponent molecular mixtures in small systems. The aim of this research is to provide new comprehensive description of small equilibrium molecular systems with numerous scientific and industrial applications for artificial and natural materials with nanopores. Several cases for molecular systems in small cavities are studied. In particular size-dependent additional pressure for small systems is evaluated analytically and numerically. The obtained results are in correspondence to published experimental data and molecular dynamics simulations. [Preview Abstract] |
Wednesday, March 4, 2015 10:36AM - 10:48AM |
L3.00014: Heterogeneous dynamics and stretched exponential decay of spatio-temporal correlations for Coulomb-interacting particles in confined geometries Amit Ghosal, Biswarup Ash, Jaydeb Chakrabarti We investigate the dynamics of Coulomb-interacting confined particles over a range of temperatures capturing the crossover from a Wigner molecule to a liquid-like phase. Dynamical signatures, derived from the Van-Hove correlations, develop pivotal understanding of the phases as well as the intervening crossover, which are inaccessible from the study of static correlations alone. The motion of the particles shows frustrations, produces heterogeneities depending on the observation time-scales and temperatures and results into a non-Gaussian behavior. The extent and nature of the departure of the behavior of spatio-temporal correlations from the conventional wisdom depends crucially on the symmetry of the confinements. In particular, we find that the decay of correlations follow a stretched-exponential form in traps that lack any symmetry. Our data offers a broad support to a theoretical model that integrates the non-Gaussian behavior arising from the convolution of Gaussian fluctuations weighted by appropriate diffusivities, consistent with local dynamics. The richness of information from the dynamic correlation will be shown to improve the understanding of melting in confined systems in a powerful manner. [Preview Abstract] |
Wednesday, March 4, 2015 10:48AM - 11:00AM |
L3.00015: Current-driven complex dynamics of single-layer epitaxial islands on substrates Dwaipayan Dasgupta, Dimitrios Maroudas We study theoretically the current-driven dynamics of isolated single-layer epitaxial islands on crystalline substrates, which provides important guidance toward surface nanopatterning approaches based on the current-driven assembly of such islands. We develop and validate a fully nonlinear model for the islands' driven morphological evolution on elastic substrates of face-centered cubic crystals in the regime where diffusional mass transport is limited to the island edge. For islands on $\left\langle {110} \right\rangle $-, $\left\langle {100} \right\rangle $-, and $\left\langle {111} \right\rangle $-oriented substrate surfaces, we report a transition in the asymptotic states reached by such driven island dynamics from steady to oscillatory, mediated by Hopf bifurcation. We characterize the bifurcation and explore the dependence of the stable time-periodic state beyond the Hopf point on the misorientation angle between the applied electric field and fast edge diffusion directions, the strength of the edge diffusional anisotropy, and the island size. For islands larger than a critical size, depending on the orientation of the substrate surface, we observe fingering and necking instabilities in the island morphology. We carry out a comprehensive numerical simulation study and explore the complexity of the driven island dynamics with the variation of the problem parameters. [Preview Abstract] |
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