6,511 research outputs found
A new 111 type iron pnictide superconductor LiFeP
A new iron pnictide LiFeP superconductor was found. The compound crystallizes
into a Cu2Sb structure containing an FeP layer showing superconductivity with
maximum Tc of 6K. This is the first 111 type iron pnictide superconductor
containing no arsenic. The new superconductor is featured with itinerant
behavior at normal state that could helpful to understand the novel
superconducting mechanism of iron pnictide compounds.Comment: 3 figures + 1 tabl
Anomalous violation of the local constant field approximation in colliding laser beams
It is commonly assumed that in ultrastrong laser fields, when the strong field parameter of the laser field is larger than one, the electron radiation is well described by the local constant field approximation (LCFA). We discuss the failure of this conjecture, considering radiation of an ultrarelativistic electron interacting with strong counterpropagating laser waves. A deviation from LCFA, in particular in the high-frequency domain, is shown to occur even at because of the appearance of an additional small time scale in the trajectory. Moreover, we identify a new class of LCFA violation, when the radiation formation length becomes smaller than the one via LCFA. It is characterized by a broad and smooth spectrum rather than an harmonic structure. A similar phenomenon is also demonstrated in the scenario of an electron colliding with an ultrashort laser pulse. The relevance to laser-plasma kinetic simulations is discussed
Tunneling ionization in ultrashort laser pulses: Edge effect and remedy
Tunneling ionization of an atom in ultrashort laser pulses is considered. When the driving laser pulse is switched-on and -off with a steep slope, the photoelectron momentum distribution (PMD) shows an edge-effect because of the photoelectron diffraction by the time-slit of the pulse. The trivial diffraction pattern of the edge effect consisting of fast oscillations in the PMD disguises in the deep nonadiabatic regime the physically more interesting features in the spectrum which originate from the photoelectron dynamics. We point out the precise conditions how to avoid this scenario experimentally and if unavoidable in theory we put forward an efficient method to remove the edge-effect in the PMD. This allows to highlight the nonadiabatic dynamical features of the PMD, which is indispensable for their further investigation in complex computationally demanding scenarios. The method is firstly demonstrated on a one-dimensional problem, and further applied in three-dimensions for the attoclock. The method is validated by a comparison of analytical results via the strong-field approximation with numerical solutions of the time-dependent Schr\"odinger equation
Ultrarelativistic electrons in counterpropagating laser beams
The dynamics and radiation of ultrarelativistic electrons in strong
counterpropagating laser beams are investigated. Assuming that the particle
energy is the dominant scale in the problem, an approximate solution of
classical equations of motion is derived and the characteristic features of the
motion are examined. A specific regime is found with comparable strong field
quantum parameters of the beams, when the electron trajectory exhibits
ultrashort spike-like features, which bears great significance to the
corresponding radiation properties. An analytical expression for the spectral
distribution of spontaneous radiation is derived in the framework of the
Baier-Katkov semiclassical approximation based on the classical trajectory. All
the analytical results are further validated by exact numerical calculations.
We consider a non-resonant regime of interaction, when the laser frequencies in
the electron rest frame are far from each other, avoiding stimulated emission.
Special attention is devoted to settings when the description of radiation via
the local constant field approximation fails and to corresponding spectral
features. Periodic and non-periodic regimes are considered, when lab
frequencies of the laser waves are always commensurate. The sensitivity of
spectra with respect to the electron beam spread, focusing and finite duration
of the laser beams is explored.Comment: 23 papes, 10 figure
High-brilliance ultra-narrow-band x-rays via electron radiation in colliding laser pulses
A setup of a unique x-ray source is put forward employing a relativistic
electron beam interacting with two counter-propagating laser pulses in the
nonlinear few-photon regime. In contrast to Compton scattering (CS) sources,
the envisaged x-ray source exhibits an extremely narrow relative bandwidth of
to , comparable to the x-ray free-electron laser (XFEL). The
brilliance of the x-rays can be orders of magnitude higher than a
state-of-the-art CS source, while the angle spreading of the radiation is much
smaller. By tuning the laser intensities and the electron energy, one can
realize either a single peak or a comb-like x-ray source around keV energy. The
laser intensity and the electron energy in the suggested setup are rather
moderate, rendering this scheme compact and table-top size, as opposed to XFEL
and synchrotron infrastructures
Pair creation for bosons in electric and magnetic fields
By solving the quantum field theoretical version of the Klein-Gordon equation numerically, we study the creation process for charged boson-antiboson pairs in static electric and magnetic fields. The fields are perpendicular to each other and spatially localized along the same direction, which permits us to study the crucial impact of the magnetic field\u27s spatial extension on dynamics. If its width is comparable to that of the electric field, we find a magnetically induced Lorentz suppression of the pair-creation process. When the width is increased such that the created bosons can revisit the interaction region, we find a region of exponential self-amplification that can be attributed to a spontaneous emissionlike enhancement. If the width is increased further, this trend is reversed and the magnetic field can even shut off the particle production completely
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