2,050 research outputs found
Stochastic Gross-Pitaevskii Equation for the Dynamical Thermalization of Bose-Einstein Condensates
We present a theory for the description of energy relaxation in a
nonequilibrium condensate of bosonic particles. The approach is based on
coupling to a thermal bath of other particles (e.g., phonons in a crystal, or
noncondensed atoms in a cold atom system), which are treated with a Monte Carlo
type approach. Together with a full account of particle-particle interactions,
dynamic driving, and particle loss, this offers a complete description of
recent experiments in which Bose-Einstein condensates are seen to relax their
energy as they propagate in real space and time. As an example, we apply the
theory to the solid-state system of microcavity exciton polaritons, in which
nonequilibrium effects are particularly prominent.Comment: Manuscript: 5 pages (Main Text) + 2 figures + 4 pages (Supplemental
Material). Proofs versio
Magnetic Field Control of the Optical Spin Hall Effect
We investigate theoretically the effect of an external magnetic field on
polarization patterns appearing in quantum microcavities due to the optical
spin Hall effect (OSHE). We show that increase of the magnetic field
perpendicular to the plane of the cavity resulting in the increase of the
Zeeman splitting leads to the transition from azimuthal separation of
polarizations to their radial separation. This effect can be straightforwardly
detected experimentally.Comment: 9 pages, 6 figure
Optomechanics with Cavity Polaritons: Dissipative Coupling and Unconventional Bistability
We study a hybrid system formed from an optomechanical resonator and a cavity
mode strongly coupled to an excitonic transition inside a quantum well. We show
that due to the mixing of cavity photon and exciton states, the emergent
quasiparticles - polaritons - possess coupling to the mechanical mode of both
dispersive and dissipative nature. We calculate the occupancies of polariton
modes and reveal bistable behavior, which deviates from conventional Kerr
nonlinearity or dispersive coupling cases due to the dissipative coupling. The
described system serves as a good candidate for future polaritonic devices and
solid state quantum information processing.Comment: 5 pages, 4 figure
Tunable single photon emission from dipolaritons
We study a system comprising of a double quantum well embedded in a
micropillar optical cavity, where strong coupling between a direct exciton,
indirect exciton, and cavity photon is achieved. We show that the resulting
hybrid quasiparticles - dipolaritons - can induce strong photon correlations
and lead to anti-bunched behaviour of the cavity output field. The origin of
the observed single photon emission is attributed to unconventional photon
blockade. Moreover, we find that the second-order equal time correlation
function can be tuned over a large range using an electric field
applied to the structure, or changing the frequency of the pump. This allows
for an on-the-flight control of cavity output properties, and is important for
the future generation of tunable single photon emission sources.Comment: 10 pages, 5 figure
Multimode entanglement in coupled cavity arrays
We study a driven-dissipative array of coupled nonlinear optical resonators
by numerically solving the Von Neumann equation for the density matrix. We
demonstrate that quantum correlated states of many photons can be generated
also in the limit where the nonlinearity is much smaller than the losses,
contrarily to common expectations. Quantum correlations in this case arise from
interference between different pathways that the system can follow in the
Hilbert space to reach its steady state under the effect of coherent driving
fields. We characterize in particular two systems: a linear chain of three
coupled cavities and an array of eight coupled cavities. We demonstrate the
existence of a parameter range where the system emits photons with
continuous-variable bipartite and quadripartite entanglement, in the case of
the first and the second system respectively. This entanglement is shown to
survive realistic rates of pure dephasing and opens a new perspective for the
realization of quantum simulators or entangled photon sources without the
challenging requirement of strong optical nonlinearities.Comment: 20 pages, 7 figure
Multivalley engineering in semiconductor microcavities
We consider exciton-photon coupling in semiconductor microcavities in which
separate periodic potentials have been embedded for excitons and photons. We
show theoretically that this system supports degenerate ground-states appearing
at non-zero in-plane momenta, corresponding to multiple valleys in reciprocal
space, which are further separated in polarization corresponding to a
polarization-valley coupling in the system. Aside forming a basis for
valleytronics, the multivalley dispersion is predicted to allow for spontaneous
momentum symmetry breaking and two-mode squeezing under non-resonant and
resonant excitation, respectively.Comment: Manuscript: 7 pages, 7 figures, published in Scientific Reports 7,
45243 (2017
Continuous THz emission from dipolaritons
We propose a scheme of continuous tunable THz emission based on dipolaritons
--- mixtures of strongly interacting cavity photons and direct excitons, where
the latter are coupled to indirect excitons via tunnelling. We investigate the
property of multistability under continuous wave (CW) pumping, and the
stability of the solutions. We establish the conditions of parametric
instability, giving rise to oscillations in density between the direct exciton
and indirect modes under CW pumping. In this way we achieve continuous and
tunable emission in the THz range in a compact single-crystal device. We show
that the emission frequency can be tuned in a certain range by varying an
applied electric field and pumping conditions. Finally, we demonstrate the
dynamic switching between different phases in our system, allowing rapid
control of THz radiation.Comment: Main article 6 pages and 5 figures, two appendices 8 pages and 2
figure
Vortices in spinor cold exciton condensates with spin-orbit interaction
We study theoretically the ground states of topological defects in a spinor
four-component condensate of cold indirect excitons. We analyze possible ground
state solutions for different configurations of vortices and half-vortices. We
show that if only Rashba or Dreselhaus spin-orbit interaction (SOI) for
electrons is present the stable states of topological defects can represent a
cylindrically symmetric half-vortex or half vortex-antivortex pairs, or a
non-trivial pattern with warped vortices. In the presence of both of Rashba and
Dresselhaus SOI the ground state of a condensate represents a stripe phase and
vortex type solutions become unstable
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