2,512 research outputs found
Hysteresis in one-dimensional reaction-diffusion systems
We introduce a simple nonequilibrium model for a driven diffusive system with
nonconservative reaction kinetics which exhibits ergodicity breaking and
hysteresis in one dimension. These phenomena can be understood through a
description of the dominant stochastic many-body dynamics in terms of an
equilibrium single-particle problem, viz. the random motion of a shock in an
effective potential. This picture also leads to the exact phase diagram of the
system and suggests a new generic mechanism for "freezing by heating".Comment: 4 Pages, 5 figure
Condensation in the zero range process: stationary and dynamical properties
The zero range process is of particular importance as a generic model for
domain wall dynamics of one-dimensional systems far from equilibrium. We study
this process in one dimension with rates which induce an effective attraction
between particles. We rigorously prove that for the stationary probability
measure there is a background phase at some critical density and for large
system size essentially all excess particles accumulate at a single, randomly
located site. Using random walk arguments supported by Monte Carlo simulations,
we also study the dynamics of the clustering process with particular attention
to the difference between symmetric and asymmetric jump rates. For the late
stage of the clustering we derive an effective master equation, governing the
occupation number at clustering sites.Comment: 22 pages, 4 figures, to appear in J. Stat. Phys.; improvement of
presentation and content of Theorem 2, added reference
Coupled NASTRAN/boundary element formulation for acoustic scattering
A coupled finite element/boundary element capability is described for calculating the sound pressure field scattered by an arbitrary submerged 3-D elastic structure. Structural and fluid impedances are calculated with no approximation other than discretization. The surface fluid pressures and normal velocities are first calculated by coupling a NASTRAN finite element model of the structure with a discretized form of the Helmholtz surface integral equation for the exterior field. Far field pressures are then evaluated from the surface solution using the Helmholtz exterior integral equation. The overall approach is illustrated and validated using a known analytic solution for scattering from submerged spherical shells
Superradiance-like Electron Transport through a Quantum Dot
We theoretically show that intriguing features of coherent many-body physics
can be observed in electron transport through a quantum dot (QD). We first
derive a master equation based framework for electron transport in the
Coulomb-blockade regime which includes hyperfine (HF) interaction with the
nuclear spin ensemble in the QD. This general tool is then used to study the
leakage current through a single QD in a transport setting. We find that, for
an initially polarized nuclear system, the proposed setup leads to a strong
current peak, in close analogy with superradiant emission of photons from
atomic ensembles. This effect could be observed with realistic experimental
parameters and would provide clear evidence of coherent HF dynamics of nuclear
spin ensembles in QDs.Comment: 21 pages, 10 figure
Hybrid Architecture for Engineering Magnonic Quantum Networks
We show theoretically that a network of superconducting loops and magnetic
particles can be used to implement magnonic crystals with tunable magnonic band
structures. In our approach, the loops mediate interactions between the
particles and allow magnetic excitations to tunnel over long distances. As a
result, different arrangements of loops and particles allow one to engineer the
band structure for the magnonic excitations. Furthermore, we show how magnons
in such crystals can serve as a quantum bus for long-distance magnetic coupling
of spin qubits. The qubits are coupled to the magnets in the network by their
local magnetic-dipole interaction and provide an integrated way to measure the
state of the magnonic quantum network.Comment: Manuscript: 4 pages, 3 figures. Supplemental Material: 9 pages, 4
figures. V2: Published version in PRA: 14 pages + 8 figures. Substantial
rearrangement of the content of the previous versio
Nuclear Spin Dynamics in Double Quantum Dots: Multi-Stability, Dynamical Polarization, Criticality and Entanglement
We theoretically study the nuclear spin dynamics driven by electron transport
and hyperfine interaction in an electrically-defined double quantum dot (DQD)
in the Pauli-blockade regime. We derive a master-equation-based framework and
show that the coupled electron-nuclear system displays an instability towards
the buildup of large nuclear spin polarization gradients in the two quantum
dots. In the presence of such inhomogeneous magnetic fields, a quantum
interference effect in the collective hyperfine coupling results in sizable
nuclear spin entanglement between the two quantum dots in the steady state of
the evolution. We investigate this effect using analytical and numerical
techniques, and demonstrate its robustness under various types of
imperfections.Comment: 35 pages, 19 figures. This article provides the full analysis of a
scheme proposed in Phys. Rev. Lett. 111, 246802 (2013). v2: version as
publishe
Boundary-induced bulk phase transition and violation of Fick's law in two-component single-file diffusion with open boundaries
We study two-component single-file diffusion inside a narrow channel that at
its ends is open and connected with particle reservoirs. Using a two-species
version of the symmetric simple exclusion process as a model, we propose a
hydrodynamic description of the coarse-grained dynamics with a self-diffusion
coefficient that is inversely proportional to the length of the channel. The
theory predicts an unexpected nonequilibrium phase transition for the bulk
particle density as the external total density gradient between the reservoirs
is varied. The individual particle currents do not in general satisfy Fick's
first law. These results are confirmed by extensive dynamical Monte-Carlo
simulations for equal diffusivities of the two components.Comment: 12 pages, 3 figure
Wigner crystals in two-dimensional transition-metal dichalcogenides: Spin physics and readout
Wigner crystals are prime candidates for the realization of regular electron
lattices under minimal requirements on external control and electronics.
However, several technical challenges have prevented their detailed
experimental investigation and applications to date. We propose an
implementation of two-dimensional electron lattices for quantum simulation of
Ising spin systems based on self-assembled Wigner crystals in transition-metal
dichalcogenides. We show that these semiconductors allow for minimally invasive
all-optical detection schemes of charge ordering and total spin. For incident
light with optimally chosen beam parameters and polarization, we predict a
strong dependence of the transmitted and reflected signals on the underlying
lattice periodicity, thus revealing the charge order inherent in Wigner
crystals. At the same time, the selection rules in transition-metal
dichalcogenides provide direct access to the spin degree of freedom via Faraday
rotation measurements.Comment: 15 pages, 12 figure
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