538 research outputs found
Quantum Electronic Transport through a Precessing Spin
The conductance through a local nuclear spin precessing in a magnetic field
is studied by using the equations-of-motion approach. The characteristics of
the conductance is determined by the tunneling matrix and the position of
equilibrium chemical potential. We find that the spin flip coupling between the
electrons on the spin site and the leads produces the conductance oscillation.
When the spin is precessing in the magnetic field at Larmor frequency
(), the conductance develops the oscillation with the frequency of
both and 2 components, the relative spectrum weight of
which can be tuned by the chemical potential and the spin flip coupling.Comment: 5 pages, 3 figure
Secondary electron emission yield in the limit of low electron energy
Secondary electron emission (SEE) from solids plays an important role in many
areas of science and technology.1 In recent years, there has been renewed
interest in the experimental and theoretical studies of SEE. A recent study
proposed that the reflectivity of very low energy electrons from solid surface
approaches unity in the limit of zero electron energy2,3,4, If this was indeed
the case, this effect would have profound implications on the formation of
electron clouds in particle accelerators,2-4 plasma measurements with
electrostatic Langmuir probes, and operation of Hall plasma thrusters for
spacecraft propulsion5,6. It appears that, the proposed high electron
reflectivity at low electron energies contradicts to numerous previous
experimental studies of the secondary electron emission7. The goal of this note
is to discuss possible causes of these contradictions.Comment: 3 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop
on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba,
Ital
Nanowire Spin Torque Oscillator Driven by Spin Orbit Torques
Spin torque from spin current applied to a nanoscale region of a ferromagnet
can act as negative magnetic damping and thereby excite self-oscillations of
its magnetization. In contrast, spin torque uniformly applied to the
magnetization of an extended ferromagnetic film does not generate
self-oscillatory magnetic dynamics but leads to reduction of the saturation
magnetization. Here we report studies of the effect of spin torque on a system
of intermediate dimensionality - a ferromagnetic nanowire. We observe coherent
self-oscillations of magnetization in a ferromagnetic nanowire serving as the
active region of a spin torque oscillator driven by spin orbit torques. Our
work demonstrates that magnetization self-oscillations can be excited in a
one-dimensional magnetic system and that dimensions of the active region of
spin torque oscillators can be extended beyond the nanometer length scale.Comment: The link to the published version is
http://www.nature.com/ncomms/2014/141205/ncomms6616/full/ncomms6616.htm
Dependence of nuclear magnetic moments on quark masses and limits on temporal variation of fundamental constants from atomic clock experiments
We calculate the dependence of the nuclear magnetic moments on the quark
masses including the spin-spin interaction effects and obtain limits on the
variation of the fine structure constant and
using recent atomic clock experiments examining hyperfine transitions in H, Rb,
Cs, Yb and Hg and the optical transition in H, Hg and Yb
h-deformation of GL(1|1)
h-deformation of (graded) Hopf algebra of functions on supergroup GL(1|1) is
introduced via a contration of GL_q (1|1). The deformation parameter h is odd
(grassmann). Related differential calculus on h-superplane is presented.Comment: latex file, 8 pages, minor change
- …