2,047 research outputs found
Strong light-matter coupling: parametric interactions in a cavity and free-space
We consider parametric interactions of laser pulses in a coherent macroscopic
ensemble of resonant atoms, which are possible in the strong coupling regime of
light-matter interaction. The spectrum condensation (lasing at collective
vacuum Rabi sidebands) was studied in an active cavity configuration.
Parametric interactions under the strong light-matter coupling were proved even
in free space. In contrast to bichromatic beats in a cavity, they were shown to
appear due to interference between polaritonic wave packets of different group
velocities.Comment: 4 pages, 2 figure
Dark polariton-solitons in semiconductor microcavities
We report the existence, symmetry breaking and other instabilities of dark
polariton-solitons in semiconductor microcavities operating in the strong
coupling regime. These half-light half-matter solitons are potential candidates
for applications in all-optical signal processing. Their excitation time and
required pump powers are a few orders of magnitude less than those of their
weakly coupled light-only counterparts.Comment: submitted to PR
Electronic structure of GaAs1-xNx alloy by soft-X-ray absorption and emission: Origin of the reduced optical efficiency
The local electronic structure of N atoms in a diluted GaAs1-xNx (x=3%)
alloy, in view of applications in optoelectronics, is determined for the first
time using soft-X-ray absorption (SXA) and emission (SXE). Deviations from
crystalline GaN, in particular in the conduction band, are dramatic. Employing
the orbital character and elemental specificity of the SXE/SXA spectroscopies,
we identify a charge transfer from the N atoms at the valence band maximum,
reducing the overlap with the wavefunction in conduction band minimum, as the
main factor limiting the optical efficiency of GaAs1-xNx alloys. Moreover, a
k-conserving process of resonant inelastic x-ray scattering involving the L1
derived valence and conduction states is discovered.Comment: 3 pages, physica status solidi (Rapid Research Notes), in pres
Superconducting transition temperatures and coherence length in non s-wave pairing materials correlated with spin-fluctuation mediated interaction
Following earlier work on electron or hole liquids flowing through assemblies
with magnetic fluctuations, we have recently exposed a marked correlation of
the superconducting temperature Tc, for non s-wave pairing materials, with
coherence length xi and effective mass m*. The very recent study of Abanov et
al. [Europhys. Lett. 54, 488 (2001)] and the prior investigation of Monthoux
and Lonzarich [Phys. Rev. B 59, 14598 (1999)] have each focussed on the concept
of a spin-fluctuation temperature T_sf, which again is intimately related to
Tc. For the d-wave pairing via antiferromagnetic spin fluctuations in the
cuprates, these studies are brought into close contact with our own work, and
the result is that k_B T_sf ~ hbar^2 / m* xi^2. This demonstrates that xi is
also determined by such antiferromagnetic spin-fluctuation mediated pair
interaction. The coherence length in units of the lattice spacing is then
essentially given in the cuprates as the square root of the ratio of two
characteristic energies, namely: the kinetic energy of localization of a charge
carrier of mass m* in a specified magnetic correlation length to the hopping
energy. The quasi-2D ruthenate Sr_2RuO_4, with Tc ~ 1.3 K, has p-wave
spin-triplet pairing and so is also briefly discussed here.Comment: Accepted for publication in Phys. Rev.
Search for Sterile Neutrinos with a Radioactive Source at Daya Bay
The far site detector complex of the Daya Bay reactor experiment is proposed
as a location to search for sterile neutrinos with > eV mass. Antineutrinos
from a 500 kCi 144Ce-144Pr beta-decay source (DeltaQ=2.996 MeV) would be
detected by four identical 20-ton antineutrino targets. The site layout allows
flexible source placement; several specific source locations are discussed. In
one year, the 3+1 sterile neutrino hypothesis can be tested at essentially the
full suggested range of the parameters Delta m^2_{new} and sin^22theta_{new}
(90% C.L.). The backgrounds from six nuclear reactors at >1.6 km distance are
shown to be manageable. Advantages of performing the experiment at the Daya Bay
far site are described
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