261,388 research outputs found
Unipolar and bipolar fatigue in antiferroelectric lead zirconate thin films and evidences for switching-induced charge injection inducing fatigue
For the first time, we show that unipolar fatigue does occur in
antiferroelectric capacitors, confirming the predictions of a previous work
[Appl. Phys. Lett., 94, 072901 (2009)]. We also show that unipolar fatigue in
antiferroelectrics is less severe than bipolar fatigue if the driving field is
of the same magnitude. This phenomenon has been attributed to the
switching-induced charge injection, the main cause for polarization fatigue in
ferroelectric and antiferroelectric materials. Other evidences for polarization
fatigue caused by the switching-induced charge injection from the nearby
electrode rather than the charge injection during stable/quasi-stable leakage
current stage are also discussed.Comment: 10 pages and 2 figure
A Memristor Model with Piecewise Window Function
In this paper, we present a memristor model with piecewise window function, which is continuously differentiable and consists of three nonlinear pieces. By introducing two parameters, the shape of this window function can be flexibly adjusted to model different types of memristors. Using this model, one can easily obtain an expression of memristance depending on charge, from which the numerical value of memristance can be readily calculated for any given charge, and eliminate the error occurring in the simulation of some existing window function models
Chaos synchronization in gap-junction-coupled neurons
Depending on temperature the modified Hodgkin-Huxley (MHH) equations exhibit
a variety of dynamical behavior including intrinsic chaotic firing. We analyze
synchronization in a large ensemble of MHH neurons that are interconnected with
gap junctions. By evaluating tangential Lyapunov exponents we clarify whether
synchronous state of neurons is chaotic or periodic. Then, we evaluate
transversal Lyapunov exponents to elucidate if this synchronous state is stable
against infinitesimal perturbations. Our analysis elucidates that with weak gap
junctions, stability of synchronization of MHH neurons shows rather complicated
change with temperature. We, however, find that with strong gap junctions,
synchronous state is stable over the wide range of temperature irrespective of
whether synchronous state is chaotic or periodic. It turns out that strong gap
junctions realize the robust synchronization mechanism, which well explains
synchronization in interneurons in the real nervous system.Comment: Accepted for publication in Phys. Rev.
Dissipation Effects in Hybrid Systems
The dissipation effect in a hybrid system is studied in this Letter. The
hybrid system is a compound of a classical magnetic particle and a quantum
single spin. Two cases are considered. In the first case, we investigate the
effect of the dissipative quantum subsystem on the motion of its classical
partner. Whereas in the second case we show how the dynamics of the quantum
single spin are affected by the dissipation of the classical particle.
Extension to general dissipative hybrid systems is discussed.Comment: 4+ pages, 4 figure
Thermodynamics of the spin-flop transition in a quantum XYZ chain
A special limit of an antiferromagnetic XYZ chain was recently shown to
exhibit interesting bulk as well as surface spin-flop transitions at T=0. Here
we provide a complete calculation of the thermodynamics of the bulk transition
using a transfer-matrix-renormalization-group (TMRG) method that addresses
directly the thermodynamic limit of quantum spin chains. We also shed some
light on certain spinwave anomalies at low temperature predicted earlier by
Johnson and Bonner.Comment: 4 pages, 6 Postscript figure
Neutrino oscillations in de Sitter space-time
We try to understand flavor oscillations and to develop the formulae for
describing neutrino oscillations in de Sitter space-time. First, the covariant
Dirac equation is investigated under the conformally flat coordinates of de
Sitter geometry. Then, we obtain the exact solutions of the Dirac equation and
indicate the explicit form of the phase of wave function. Next, the concise
formulae for calculating the neutrino oscillation probabilities in de Sitter
space-time are given. Finally, The difference between our formulae and the
standard result in Minkowski space-time is pointed out.Comment: 13 pages, no figure
Geometric phase in dephasing systems
Beyond the quantum Markov approximation, we calculate the geometric phase of
a two-level system driven by a quantized magnetic field subject to phase
dephasing. The phase reduces to the standard geometric phase in the weak
coupling limit and it involves the phase information of the environment in
general. In contrast with the geometric phase in dissipative systems, the
geometric phase acquired by the system can be observed on a long time scale. We
also show that with the system decohering to its pointer states, the geometric
phase factor tends to a sum over the phase factors pertaining to the pointer
states.Comment: 4 page
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