279,955 research outputs found
Schiff Screening of Relativistic Nucleon Electric-Dipole Moments by Electrons
We show, at leading-order in the multipole expansion of the electron-nucleus
interaction, that nucleon electric-dipole moments are completely shielded by
electrons so that they contribute nothing to atomic electric-dipole moments,
even when relativity in the nucleus is taken into account. It is well known
that relativistic electron motion, by contrast, leads to dipole moments that
are not screened; we discuss the reasons for the difference.Comment: 4 pages, typeset by REVTeX, submitted to PR
Nanoscopic processes of Current Induced Switching in thin tunnel junctions
In magnetic nanostructures one usually uses a magnetic field to commute
between two resistance (R) states. A less common but technologically more
interesting alternative to achieve R-switching is to use an electrical current,
preferably of low intensity. Such Current Induced Switching (CIS) was recently
observed in thin magnetic tunnel junctions, and attributed to electromigration
of atoms into/out of the insulator. Here we study the Current Induced
Switching, electrical resistance, and magnetoresistance of thin
MnIr/CoFe/AlO/CoFe tunnel junctions. The CIS effect at room temperature
amounts to 6.9% R-change between the high and low states and is attributed to
nanostructural rearrangements of metallic ions in the electrode/barrier
interfaces. After switching to the low R-state some electro-migrated ions
return to their initial sites through two different energy channels. A low
(high) energy barrier of 0.13 eV (0.85 eV) was estimated. Ionic
electromigration then occurs through two microscopic processes associated with
different types of ions sites/defects. Measurements under an external magnetic
field showed an additional intermediate R-state due to the simultaneous
conjugation of the MR (magnetic) and CIS (structural) effects.Comment: 6 pages, 4 figure
Asymmetric Avalanches in the Condensate of a Zeeman-limited Superconductor
We report the non-equilibrium behavior of disordered superconducting Al films
in high Zeeman fields. We have measured the tunneling density of states of the
films through the first-order Zeeman critical field transition. We find that
films with sheet resistances of a few hundred ohms exhibit large avalanche-like
collapses of the condensate on the superheating branch of the critical field
hysteresis loop. In contrast, the transition back into the superconducting
phase (i.e., along the supercooling branch) is always continuous. The fact that
the condensate follows an unstable trajectory to the normal state suggests that
the order parameter in the hysteretic regime is not homogeneous.Comment: 5 pages, 5 figures, to appear in PR
Certain comments on the application of the method of averaging to the study of the rotational motions of a triaxial rigid body
Averaging technique applied to variational equations describing rotational motions of rigid triaxial body in elliptical orbi
The role of attractive forces in viscous liquids
We present evidence from computer simulation that the slowdown of relaxation
of a standard Lennard-Jones glass-forming liquid and that of its reduction to a
model with truncated pair potentials without attractive tails is quantitatively
and qualitatively different in the viscous regime. The pair structure of the
two models is however very similar. This finding, which appears to contradict
the common view that the physics of dense liquids is dominated by the steep
repulsive forces between atoms, is characterized in detail, and its
consequences are explored. Beyond the role of attractive forces themselves, a
key aspect in explaining the differences in the dynamical behavior of the two
models is the truncation of the interaction potentials beyond a cutoff at
typical interatomic distance. This leads us to question the ability of the
jamming scenario to describe the physics of glass-forming liquids and polymers.Comment: 13 pages, 12 figure
Further comments on the application of the method of averaging to the study of the rotational motions of a triaxial rigid body, part 2
The second and final step in the development of first-order secular solutions to rotational motions of triaxial bodies is presented
Quantum-mechanical communication theory
Optimum signal reception using quantum-mechanical communication theor
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