679 research outputs found
Gauge invariance and the interpretation of inter- and intraband processes in high-order harmonic generation from bulk solids
A theoretical model for high-order harmonic generation (HHG) in bulk solids
is considered. Our approach treats laser-induced inter- and intraband currents
on an equal footing. The sum of these currents is the source of the high-order
harmonic radiation, and does not depend on the particular electromagnetic gauge
we choose to describe the process. On the other hand, as it is shown using
analytic and numerical calculations, the distinction between intra- and
interband dynamics is gauge dependent, implying that the interpretation of the
process of HHG using these terms requires carefulness.Comment: 6 pages, 1 figur
Oscillating spin-orbit interaction as a source of spin-polarized wave packets in two-terminal nanoscale devices
Ballistic transport through nanoscale devices with time-dependent Rashba-type
spin-orbit interaction (SOI) can lead to spin-polarized wave packets that
appear even for completely unpolarized input. The SOI that oscillates in a
finite domain generates density and spin polarization fluctuations that leave
the region as propagating waves. Particularly, spin polarization has space and
time dependence even in regions without SOI. Our results are based on an
analytic solution of the time-dependent Schr\"odinger equation. The relevant
Floquet quasi-energies that are obtained appear in the energy spectrum of both
the transmitted and reflected waves.Comment: 13 pages, 5 figures (IOP preprint style); v2: 15 pages and 6 figures.
Subsec. 3.4, a figure and new references have been adde
Correlations between the final momenta of electrons and their initial phase-space distribution in the process of tunnel ionization
We present both full quantum mechanical and semiclassical calculations of
above threshold ionization (ATI) of a hydrogen atom in the tunneling regime by
a few-cycle linearly polarized infrared laser pulse. As a quantum treatment, we
applied the direct integration of the time dependent Schr\"odinger equation
(TDSE). In the semiclassical approximation (SCA), it is assumed that wavepacket
propagation in the post-tunneling process can be well described within the
classical framework. With these two methods, we analyze the similarities and
deviations for ionization of the hydrogen atom. We found that the 3 dimensional
semiclassical method can describe reasonably well the momentum correlation
pattern of the ATI peaks. We also show good agreement between the results
obtained by TDSE method and the semi-classical method. Furthermore, with the
semiclassical approximation we clearly identify and separate the regions in
momentum distributions of the ejected electrons according to initial
conditions. We illustrate the corresponding regions with typical electron
trajectories.Comment: 7 pages, 6 figure
The effect of dynamical Bloch oscillations on optical-field-induced current in a wide gap dielectric
We consider the motion of charge carriers in a bulk wide-gap dielectric
interacting with a few-cycle laser pulse. A semiclassical model based on Bloch
equations is applied to describe the emerging time-dependent macroscopic
currents for laser intensities approaching the damage threshold. At such laser
intensities, electrons can reach edges of the first Brillouin zone even for
electron-phonon scattering rates as high as those known for SiO_2. We find
that, whenever this happens, Brag-like reflections of electron waves, also
known as Bloch oscillations, affect the dependence of the charge displaced by
the laser pulse on its carrier-envelope phase.Comment: This version corrects a mistake in the paper published by the New
Journal of Physics: panel (a) of Fig. 9 depicts -s(t_0=0) rather than
s(t_0=0
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