30,699 research outputs found
Determination of Carrier-Envelope Phase of Relativistic Few-Cycle Laser Pulses by Thomson Backscattering Spectroscopy
A novel method is proposed to determine the carrier-envelope phase (CEP) of a
relativistic few-cycle laser pulse via the central frequency of the isolated
light generated from Thomson backscattering (TBS). We theoretically investigate
the generation of a uniform flying mirror when a few-cycle drive pulse with
relativistic intensity (I > 10^{18} {{\rm{W}} \mathord{/
{\vphantom {{\rm{W}} {{\rm{cm}}^{\rm{2}}}}}.
\kern-\nulldelimiterspace} {{\rm{cm}}^{\rm{2}}}}) interacts with a target
combined with a thin and a thick foil. The central frequency of the isolated
TBS light generated from the flying mirror shows a sensitive dependence on the
CEP of the drive pulse. The obtained results are verified by one dimensional
particle in cell (1D-PIC) simulations
On the conservation of spin currents in spin-orbit coupled systems
Applying the Gordon-decomposition-like technique, the convective spin current
(CSC) is extracted from the total angular-momentum current. The CSC describes
the transport properties of the electron spin and is conserved in the
relativistic quantum mechanics approach where the spin-orbit coupling has been
intrinsically taken into account. Arrestingly, in the presence of external
electromagnetic field, the component of the convective spin along the field
remain still conserved. This conserved CSC is also derived for the first time
in the nonrelativistic limit using the Foldy-Wouthuysen transformation.Comment: 5 pages, RevTeX
Optical supercavitation in soft-matter
We investigate theoretically, numerically and experimentally nonlinear
optical waves in an absorbing out-of-equilibrium colloidal material at the
gelification transition. At sufficiently high optical intensity, absorption is
frustrated and light propagates into the medium. The process is mediated by the
formation of a matter-shock wave due to optically induced thermodiffusion, and
largely resembles the mechanism of hydrodynamical supercavitation, as it is
accompanied by a dynamic phase-transition region between the beam and the
absorbing material.Comment: 4 pages, 5 figures, revised version: corrected typos and reference
Entanglement, subsystem particle numbers and topology in free fermion systems
We study the relationship between bipartite entanglement, subsystem particle
number and topology in a half-filled free fermion system. It is proposed that
the spin-projected particle numbers can distinguish the quantum spin Hall state
from other states, and can be used to establish a new topological index for the
system. Furthermore, we apply the new topological invariant to a disordered
system and show that a topological phase transition occurs when the disorder
strength is increased beyond a critical value. It is also shown that the
subsystem particle number fluctuation displays behavior very similar to that of
the entanglement entropy. This provides a lower-bound estimation for the
entanglement entropy, which can be utilized to obtain an estimate of the
entanglement entropy experimentally.Comment: 14 pages, 6 figure
Giant Enhancement of Surface Second Harmonic Generation in BaTiO_3 due to Photorefractive Surface Wave Excitation
We report observation of strongly enhanced surface SHG in BaTiO_3 due to
excitation of a photorefractive surface electromagnetic wave. Surface SH
intensity may reach 10^{-2} of the incident fundamental light intensity.
Angular, crystal orientation and polarization dependencies of this SHG are
presented. Possible applications of this effect in nonlinear surface
spectroscopy are discussed.Comment: 5 pages, 6 figures, submitted to Physical Review Letters on the
3/29/199
Aging of the Nonlinear Optical Susceptibility of colloidal solutions
Using Z-scan and dynamic light scattering measurements we investigate the
nonlinear optics response of a colloidal solution undergoing dynamics slowing
down with age. We study the high optical nonlinearity of an organic dye
(Rhodamine B) dispersed in a water-clay (Laponite) solution, at different clay
concentrations (2.0 wt% - 2.6 wt%), experiencing the gelation process. We
determine the clay platelets self diffusion coefficient and, by its comparison
with the structural relaxation time, we conclude that the gelation process
proceeds through the structuring of interconnecting clay platelets network
rather than through clusters growth and aggregation.Comment: 4 figures, 4 page
Doping induced metal-insulator transition in two-dimensional Hubbard, , and extended Hubbard, , models
We show numerically that the nature of the doping induced metal-insulator
transition in the two-dimensional Hubbard model is radically altered by the
inclusion of a term, , which depends upon a square of a single-particle
nearest-neighbor hopping. This result is reached by computing the localization
length, , in the insulating state. At finite values of we find
results consistent with where is
the critical chemical potential. In contrast, for the Hubbard model. At finite values of , the presented
numerical results imply that doping the antiferromagnetic Mott insulator leads
to a superconductor.Comment: 19 pages (latex) including 7 figures in encapsulated postscript
format. Submitted for publication in Phys. Rev.
Global axisymmetric stability analysis for a composite system of two gravitationally coupled scale-free discs
In a composite system of gravitationally coupled stellar and gaseous discs,
we perform linear stability analysis for axisymmetric coplanar perturbations
using the two-fluid formalism. The background stellar and gaseous discs are
taken to be scale-free with all physical variables varying as powers of
cylindrical radius with compatible exponents. The unstable modes set in as
neutral modes or stationary perturbation configurations with angular frequency
.Comment: 7 pages using AAS styl
Magnetodielectric effect and optic soft mode behaviour in quantum paraelectric EuTiO3 ceramics
Infrared reflectivity and time-domain terahertz transmission spectra of
EuTiO3 ceramics revealed a polar optic phonon at 6 - 300K, whose softening is
fully responsible for the recently observed quantum paraelectric behaviour.
Even if our EuTiO3 ceramics show lower permittivity than the single crystal due
to a reduced density and/or small amount of secondary pyrochlore Eu2Ti2O7
phase, we confirmed the magnetic field dependence of the permittivity, also
slightly smaller than in single crystal. Attempt to reveal the soft phonon
dependence at 1.8K on the magnetic field up to 13T remained below the accuracy
of our infrared reflectivity experiment
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