2,629 research outputs found
Exact Moving and Stationary Solutions of a Generalized Discrete Nonlinear Schrodinger Equation
We obtain exact moving and stationary, spatially periodic and localized
solutions of a generalized discrete nonlinear Schr\"odinger equation. More
specifically, we find two different moving periodic wave solutions and a
localized moving pulse solution. We also address the problem of finding exact
stationary solutions and, for a particular case of the model when stationary
solutions can be expressed through the Jacobi elliptic functions, we present a
two-point map from which all possible stationary solutions can be found.
Numerically we demonstrate the generic stability of the stationary pulse
solutions and also the robustness of moving pulses in long-term dynamics.Comment: 22 pages, 7 figures, to appear in J. Phys.
AC Josephson properties of phase slip lines in wide tin films
Current steps in the current-voltage characteristics of wide superconducting
Sn films exposed to a microwave irradiation were observed in the resistive
state with phase slip lines. The behaviour of the magnitude of the steps on the
applied irradiation power was found to be similar to that for the current steps
in narrow superconducting channels with phase slip centers and, to some extent,
for the Shapiro steps in Josephson junctions. This provides evidence for the
Josephson properties of the phase slip lines in wide superconducting films and
supports the assumption about similarity between the processes of phase slip in
wide and narrow films.Comment: 7 pages, 2 figures, to be published in Supercond. Sci. Techno
Random anisotropy disorder in superfluid 3He-A in aerogel
The anisotropic superfluid 3He-A in aerogel provides an interesting example
of a system with continuous symmetry in the presence of random anisotropy
disorder. Recent NMR experiments allow us to discuss two regimes of the
orientational disorder, which have different NMR properties. One of them, the
(s)-state, is identified as the pure Larkin-Imry-Ma state. The structure of
another state, the (f)-state, is not very clear: probably it is the
Larkin-Imry-Ma state contaminated by the network of the topological defects
pinned by aerogel.Comment: JETP Lett. style, 6 pages, no figures, discussion extended,
references added, version to be published in JETP Letter
Superflow-Stabilized Nonlinear NMR in Rotating 3He-B
Nonlinear spin precession has been observed in 3He-B in large counterflow of
the normal and superfluid fractions. The new precessing state is stabilized at
high rf excitation level and displays frequency-locked precession over a large
range of frequency shifts, with the magnetization at its equilibrium value.
Comparison to analytical and numerical calculation indicates that in this state
the orbital angular momentum L of the Cooper pairs is oriented transverse to
the external magnetic field in a ``non-Leggett'' configuration with broken
spin-orbit coupling. The resonance shift depends on the tipping angle theta of
the magnetization as omega - omega_L = (Omega_B^2 / 2 omega_L)(cos(theta) -
1/5). The phase diagram of the precessing modes with arbitrary orientation of L
is constructed.Comment: Revtex file, 5 pages, 4 figures, version submitted to Phys. Rev. Let
Multiphoton antiresonance
We show that nonlinear response of a quantum oscillator displays antiresonant
dips and resonant peaks with varying frequency of the driving field. The effect
is a consequence of special symmetry and is related to resonant multiphoton
mixing of several pairs of oscillator states at a time. We discuss the
possibility to observe the antiresonance and the associated multiphoton Rabi
oscillations in Josephson junctions.Comment: 4 pages, 3 figures; corrected referenc
Qubit state detection using the quantum Duffing oscillator
We introduce a detection scheme for the state of a qubit, which is based on
resonant few-photon transitions in a driven nonlinear resonator. The latter is
parametrically coupled to the qubit and is used as its detector. Close to the
fundamental resonator frequency, the nonlinear resonator shows sharp resonant
few-photon transitions. Depending on the qubit state, these few-photon
resonances are shifted to different driving frequencies. We show that this
detection scheme offers the advantage of small back action, a large
discrimination power with an enhanced read-out fidelity, and a sufficiently
large measurement efficiency. A realization of this scheme in the form of a
persistent current qubit inductively coupled to a driven SQUID detector in its
nonlinear regime is discussed.Comment: 10 pages, 6 figures. To appear in Phys. Rev.
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