1,744 research outputs found
Self-organized escape of oscillator chains in nonlinear potentials
We present the noise free escape of a chain of linearly interacting units
from a metastable state over a cubic on-site potential barrier. The underlying
dynamics is conservative and purely deterministic. The mutual interplay between
nonlinearity and harmonic interactions causes an initially uniform lattice
state to become unstable, leading to an energy redistribution with strong
localization. As a result a spontaneously emerging localized mode grows into a
critical nucleus. By surpassing this transition state, the nonlinear chain
manages a self-organized, deterministic barrier crossing. Most strikingly,
these noise-free, collective nonlinear escape events proceed generally by far
faster than transitions assisted by thermal noise when the ratio between the
average energy supplied per unit in the chain and the potential barrier energy
assumes small values
Constraining short-range spin-dependent forces with polarized helium 3 at the Laue-Langevin Institute
We have searched for a short-range spin-dependent interaction mediated by a
hypothetical light scalar boson with CP-violating couplings to the neutron
using the spin relaxation of hyperpolarized He. The walls of the He
cell would generate a depolarizing pseudomagnetic field.Comment: Twelfth Conference on the Intersections of Particle and Nuclear
Physics (CIPANP2015), Vail Marriott Mountain Resort, Vail, Colorado, US
On the Mass Eigenstate Composition of the 8B Neutrinos from the Sun
The present data of gallium experiments provide indirectly the only
experimental limit on the fraction of mass eigenstate for the B
neutrinos from the Sun. However, if to use the experimental data alone, the
fraction of and, consequently, still is allowed to
be varied within a rather broad range. The further experimental efforts are
needed to clear this point.Comment: 13 pages, 1 figure, 1 table. Corrected version, published in
JCAP04(2007)00
Collective Spin-Density-Wave Response Perpendicular to the Chains of the Quasi One-Dimensional Conductor (TMTSF)2PF6
Microwave experiments along all three directions of the spin-density-wave
model compound (TMTSF)PF reveal that the pinned mode resonance is
present along the and axes. The collective transport is
considered to be the fingerprint of the condensate. In contrast to common quasi
one-dimensional models, the density wave also slides in the perpendicular
direction. The collective response is absent along the least
conducting direction.Comment: 3 pages, 4 figure
Non-equilibrium Magnetization Dynamics in the Fe_8 Single-Molecule Magnet Induced by High-Intensity Microwave Radiation
Resonant microwave radiation applied to a single crystal of the molecular
magnet Fe_8 induces dramatic changes in the sample's magnetization. Transitions
between excited states are found even though at the nominal system temperature
these levels have negligible population. We find evidence that the sample heats
significantly when the resonance condition is met. In addition, heating is
observed after a short pulse of intense radiation has been turned off,
indicating that the spin system is out of equilibrium with the lattice.Comment: Version to appear in Europhysics Letters. Minor changes and updated
reference
Quantum computing on long-lived donor states of Li in Si
We predict a gigantically long lifetime of the first excited state of an
interstitial lithium donor in silicon. The nature of this effect roots in the
anomalous level structure of the {\em 1s} Li manifold under external stress.
Namely, the coupling between the lowest two states of the opposite parity is
very weak and occurs via intervalley phonon transitions only. We propose to use
these states under the controlled ac and dc stress to process quantum
information. We find an unusual form of the elastic-dipole interaction between
%the electronic transitions in different donors. This interaction scales with
the inter-donor distance as or for the transitions
between the states of the same or opposite parity, respectively. The long-range
interaction provides a high fidelity mechanism for 2-qubit operations
Stress induced dislocation roughening -- phase transition in 1d at finite temperature
We present an example of a generically forbidden phase transition in 1d at
finite temperature -- stress induced and thermally assisted roughening of a
superclimbing dislocation in a Peierls potential. We also argue that such
roughening is behind the strong suppression of the superflow through solid \he4
in a narrow temperature range recently observed by Ray and Hallock (Phys.Rev.
Lett. {\bf 105}, 145301 (2010)).Comment: 4 revtex pages, 5 figures. Replaced with the published versio
Spin-polarized current and tunnel magnetoresistance in heterogeneous single-barrier magnetic tunnel junctions
© 2016 Elsevier B.V. All rights reserved. Current in heterogeneous tunnel junctions is studied in the framework of the parabolic conduction-band model. The developed model of the electron tunneling takes explicitly into account the difference of effective masses between ferromagnetic and insulating layers and between conduction subbands. Calculations for Fe/MgO/Fe-like structures have shown the essential impact of effective mass differences in regions (constituents) of the structure on the tunnel magnetoresistance of the junction
The role of Helium-3 impurities in the stress induced roughening of superclimbing dislocations in solid Helium-4
We analyze the stress induced and thermally assisted roughening of a forest
of superclimbing dislocations in a Peierls potential in the presence of
Helium-3 impurities and randomly frozen in static stresses. It is shown that
the temperature of the dip in the flow rate observed by Ray and Hallock
(Phys.Rev. Lett. {\bf 105}, 145301 (2010)) is determined by the energy of the
impurity activation from dislocation core. However, it is suppressed by,
essentially, the logarithm of the impurity fraction. The width of the dip is
determined by inhomogeneous fluctuations of the stresses and is shown to be
much smaller than .Comment: Submitted to the LT26-conference proceeding
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