140 research outputs found
Oblique Half-Solitons and their Generation in Exciton-Polariton Condensates
We describe oblique half-solitons, a new type of topological defects in a two
dimensional spinor Bose Einstein condensate. A realistic protocol based on the
optical spin Hall effect is proposed toward their generation within an
exciton-polariton system.Comment: 4 Pages, 3 Figure
Effect of TE-TM Splitting on the topological stability of half-vortices in exciton-polariton condensates
Half-vortices have been recently shown to be the elementary topological
defects supported by a spinor cavity exciton-polaritons condensates with spin
anisotropic interactions (Y. G. Rubo, Phys. Rev. Lett. 99, 106401 (2007)). A
half vortex is composed by an integer vortex for one circular component of the
condensate, whereas the other component remain static. We analyze theoretically
the effect of the splitting between TE and TM polarized eigen modes on the
structure of the vortices in this system. For TE and TM modes, the polarization
states depend on the direction of propagations of particles and imposes some
well defined phase relation between the two circular component. As a result
elementary topogical defects in this system are no more half vortices but
integer vortices correspond to an integer vortex for both circular components
of the condensate. The intrinsic life time of half vortices is given and the
texture of a few vortex states is analyzed.Comment: 9 pages, 5 figure
Entangled photons from a strongly coupled quantum dot-cavity system
A quantum dot strongly coupled to a photonic crystal has been recently
proposed as a source of entangled photon pairs [R. Johne et al., Phys. Rev.
Lett. 100, 240404 (2008)]. The biexction decay via intermediate polariton
states can be used to overcome the natural splitting between the exciton states
coupled to the horizontally and vertically polarized light modes, so that high
degrees of entanglement can be expected. We investigate theoretically the
features of realistic dot-cavity systems, including the effect of the different
oscillator strength of excitons resonances coupled to the different
polarizations of light. We show that in this case, an independent adjustment of
the cavity resonances is needed in order to keep a high entanglement degree. We
also consider the case when the biexciton-exciton transition is also strongly
coupled to a cavity mode. We show that a very fast emission rate can be
achieved allowing the repetition rates in the THz range. Such fast emission
should however be paid for by a very complex tuning of the many strongly
coupled resonances involved and by a loss of quantum efficiency. Altogether a
strongly coupled dot-cavity system seems to be very promising as a source of
entangled photon pairs.Comment: 7 pages, 5 figure
Direct observation of Dirac cones and a flatband in a honeycomb lattice for polaritons
Two-dimensional lattices of coupled micropillars etched in a planar
semiconductor microcavity offer a workbench to engineer the band structure of
polaritons. We report experimental studies of honeycomb lattices where the
polariton low-energy dispersion is analogous to that of electrons in graphene.
Using energy-resolved photoluminescence we directly observe Dirac cones, around
which the dynamics of polaritons is described by the Dirac equation for
massless particles. At higher energies, we observe p orbital bands, one of them
with the nondispersive character of a flatband. The realization of this
structure which holds massless, massive and infinitely massive particles opens
the route towards studies of the interplay of dispersion, interactions, and
frustration in a novel and controlled environment
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