2,116 research outputs found
The anomalous Hall conductivity due to the vector spin chirality
We study theoretically the anomalous Hall effect due to the vector spin
chirality carried by the local spins in the - model. We will show that
the vector spin chirality indeed induces local Hall effect in the presence of
the electron spin polarization, while the global Hall effect vanishes if
electron transport is homogeneous. This anomalous Hall effect can be
interpreted in terms of the rotational component of the spin current associated
with the vector chirality.Comment: 12 pages, 5 figure
Ultrafast magnetic vortex core switching driven by topological inverse Faraday effect
We present a theoretical discovery of an unconventional mechanism of inverse
Faraday effect (IFE) which acts selectively on topological magnetic structures.
The effect, topological inverse Faraday effect (TIFE), is induced by spin
Berry's phase of the magnetic structure when a circularly polarized light is
applied. Thus a spin-orbit interaction is not necessary unlike in the
conventional IFE. We demonstrate by numerical simulation that TIFE realizes
ultrafast switching of a magnetic vortex within a switching time of 150 ps
without magnetic field.Comment: 11 pages, 4 figure
Effects of Domain Wall on Electronic Transport Properties in Mesoscopic Wire of Metallic Ferromagnets
We study the effect of the domain wall on electronic transport properties in
wire of ferromagnetic 3 transition metals based on the linear response
theory. We considered the exchange interaction between the conduction electron
and the magnetization, taking into account the scattering by impurities as
well. The effective electron-wall interaction is derived by use of a local
gauge transformation in the spin space. This interaction is treated
perturbatively to the second order. The conductivity contribution within the
classical (Boltzmann) transport theory turns out to be negligiblly small in
bulk magnets, due to a large thickness of the wall compared with the fermi
wavelength. It can be, however, significant in ballistic nanocontacts, as
indicated in recent experiments. We also discuss the quantum correction in
disordered case where the quantum coherence among electrons becomes important.
In such case of weak localization the wall can contribute to a decrease of
resistivity by causing dephasing. At lower temperature this effect grows and
can win over the classical contribution, in particular in wire of diameter
, being the inelastic diffusion
length. Conductance change of the quantum origin caused by the motion of the
wall is also discussed.Comment: 30 pages, 4 figures. Detailed paper of Phys. Rev. Lett. 78, 3773
(1997). Submitted to J. Phys. Soc. Jp
Triggered Population III star formation: the effect of H self-shielding
The multiplicity of metal-free (Population III) stars may influence their
feedback efficiency within their host dark matter halos, affecting subsequent
metal enrichment and the transition to galaxy formation. Radiative feedback
from massive stars can trigger nearby star formation in dense self-shielded
clouds. In model radiation self-shielding, the H column density must be
accurately computed. In this study, we compare two local approximations based
on the density gradient and Jeans length with a direct integration of column
density along rays. After the primary massive star forms, we find that no
secondary stars form for both the direct integration and density gradient
approaches. The approximate method reduces the computation time by a factor of
2. The Jeans length approximation overestimates the H column density by a
factor of 10, leading to five numerically enhanced self-shielded, star-forming
clumps. We conclude that the density gradient approximation is sufficiently
accurate for larger volume galaxy simulations, although one must still caution
that the approximation cannot fully reproduce the result of direct integration.Comment: 14 pages, 7 figures, 3 tables, accepted to MNRA
Diffusive versus local spin currents in dynamic spin pumping systems
Using microscopic theory, we investigate the properties of a spin current
driven by magnetization dynamics. In the limit of smooth magnetization texture,
the dominant spin current induced by the spin pumping effect is shown to be the
diffusive spin current, i.e., the one arising from only a diffusion associated
with spin accumulation. That is to say, there is no effective field that
locally drives the spin current. We also investigate the conversion mechanism
of the pumped spin current into a charge current by spin-orbit interactions,
specifically the inverse spin Hall effect. We show that the spin-charge
conversion does not always occur and that it depends strongly on the type of
spin-orbit interaction. In a Rashba spin-orbit system, the local part of the
charge current is proportional to the spin relaxation torque, and the local
spin current, which does not arise from the spin accumulation, does not play
any role in the conversion. In contrast, the diffusive spin current contributes
to the diffusive charge current. Alternatively, for spin-orbit interactions
arising from random impurities, the local charge current is proportional to the
local spin current that constitutes only a small fraction of the total spin
current. Clearly, the dominant spin current (diffusive spin current) is not
converted into a charge current. Therefore, the nature of the spin current is
fundamentally different depending on its origin and thus the spin transport and
the spin-charge conversion behavior need to be discussed together along with
spin current generation
Relation between the Dynamics of the Reduced Purity and Correlations
A general property of the relation between the dynamics of the reduced purity
and correlations is investigated in quantum mechanical systems. We show that a
non-zero time-derivative of the reduced purity of a system implies the
existence of non-zero correlations with its environment under any unbounded
Hamiltonians with finite variance. This shows the role of local dynamical
information on the correlations, as well as the role of correlations in the
mechanism of purity change.Comment: 7 page
Hydrogen Spectroscopy with a Lamb-shift Polarimeter - An Alternative Approach Towards Anti-Hydrogen Spectroscopy Experiments
A Lamb-shift polarimeter, which has been built for a fast determination of
the polarization of protons and deuterons of an atomic-beam source and which is
frequently used in the ANKE experiment at COSY-J\"ulich, is shown to be an
excellent device for atomic-spectroscopy measurements of metastable hydrogen
isotopes. It is demonstrated that magnetic and electric dipole transitions in
hydrogen can be measured as a function of the external magnetic field, giving
access to the full Breit-Rabi diagram for the and the
states. This will allow the study of hyperfine structure, factors and the
classical Lamb shift. Although the data are not yet competitive with
state-of-the-art measurements, the potential of the method is enormous,
including a possible application to anti-hydrogen spectroscopy.Comment: 6 pages, 7 figures, accepted by European Physical Journal
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