arXiv subjects

D. D. Solnyshkov

Publications and source records attributed to D. D. Solnyshkov.

At least 55 records · Page 3Linked to original sources

arXiv2014

Engineering spin-orbit coupling for photons and polaritons in microstructures

One of the most fundamental properties of electromagnetism and special relativity is the coupling between the spin of an electron and its orbital motion. This is at the origin of the fine structure in atoms, the spin Hall effect in semiconductors, and underlies many intriguing properties of topological insulators, in particular their chiral edge states. Configurations where neutral particles experience an effective spin-orbit coupling have been recently proposed and realized using ultracold atoms and photons. Here we use coupled micropillars etched out of a semiconductor microcavity to engineer a spin-orbit Hamiltonian for photons and polaritons in a microstructure. The coupling between the spin and orbital momentum arises from the polarisation dependent confinement and tunnelling of photons between micropillars arranged in the form of a hexagonal photonic molecule. Dramatic consequences of the spin-orbit coupling are experimentally observed in these structures in the wavefunction of polariton condensates, whose helical shape is directly visible in the spatially resolved polarisation patterns of the emitted light. The strong optical nonlinearity of polariton systems suggests exciting perspectives for using quantum fluids of polaritons11 for quantum simulation of the interplay between interactions and spin-orbit coupling.

cond-mat.mes-hall↗

arXiv2014

Annular Vortex Chain in a Resonantly Pumped Polariton Superfluid

We report the formation of a ring-shaped array of vortices after injection of angular momentum in a polariton superfluid. The angular momentum is injected by a $\ell= 8$ Laguerre-Gauss beam, whereas the global rotation of the fluid is hindered by a narrow Gaussian beam placed at its center. In the linear regime a spiral interference pattern containing phase defects is visible. In the nonlinear (superfluid) regime, the interference disappears and the vortices nucleate as a consequence of the angular momentum quantization. The radial position of the vortices evolves freely in the region between the two pumps as a function of the density. Hydrodynamic instabilities resulting in the spontaneous nucleation of vortex-antivortex pairs when the system size is sufficiently large confirm that the vortices are not constrained by interference when nonlinearities dominate the system.

cond-mat.other↗

arXiv2014

Non-Abelian Gauge Fields in Photonic Cavities and Photonic Superfluids

We show that the interplay between the structure anisotropy and the energy splitting between the TE and TM modes of a microcavity leads to the appearance of a gauge field for a propagating polariton condensate. This field is analog with a spin-orbit coupling and the field texture can be tuned by rotating the sample and ranges continuously from a Rashba to a monopolar field. In the linear regime, the monopolar field leads to a remarkable focusing effect. In the interacting regime, the effective spin-orbit coupling induces a breakdown of superfluidity. The spatially homogeneous flows become unstable and dynamically evolve into textured ground states such as stripes and domain walls.

cond-mat.quant-gas↗

arXiv2014

Comment on "Linear wave dynamics explains observations attributed to dark-solitons in a polariton quantum fluid"

In a recent preprint (arXiv:1401.1128v1) Cilibrizzi and co-workers report experiments and simulations showing the scattering of polaritons against a localised obstacle in a semiconductor microcavity. The authors observe in the linear excitation regime the formation of density and phase patterns reminiscent of those expected in the non-linear regime from the nucleation of dark solitons. Based on this observation, they conclude that previous theoretical and experimental reports on dark solitons in a polariton system should be revised. Here we comment why the results from Cilibrizzi et al. take place in a very different regime than previous investigations on dark soliton nucleation and do not reproduce all the signatures of its rich nonlinear phenomenology. First of all, Cilibrizzi et al. consider a particular type of radial excitation that strongly determines the observed patterns, while in previous reports the excitation has a plane-wave profile. Most importantly, the nonlinear relation between phase jump, soliton width and fluid velocity, and the existence of a critical velocity with the time-dependent formation of vortex-antivortex pairs are absent in the linear regime. In previous reports about dark soliton and half-dark soliton nucleation in a polariton fluid, the distinctive dark soliton physics is supported both by theory (analytical and numerical) and experiments (both continuous wave and pulsed excitation).

physics.optics↗

arXiv2014

Hybrid Boltzmann Gross-Pitaevskii Theory of Bose-Einstein Condensation and Superfluidity in Open Driven-Dissipative Systems

We derive a theoretical model which describes Bose-Einstein condensation in an open driven-dissipative system. It includes external pumping of a thermal reservoir, finite life time of the condensed particles and energy relaxation. The coupling between the reservoir and the condensate is described with semi-classical Boltzmann rates. This results in a dissipative term in the Gross-Pitaevskii equation for the condensate, which is proportional to the energy of the elementary excitations of the system. We analyse the main properties of a condensate described by this hybrid Boltzmann Gross-Pitaevskii model, namely, dispersion of the elementary excitations, bogolon distribution function, first order coherence, dynamic and energetic stability, drag force created by a disorder potential. We find that the dispersion of the elementary excitations of a condensed state fulfils the Landau criterion of superfluidity. The condensate is dynamically and energetically stable as longs it moves at a velocity smaller than the speed of excitations. First order spatial coherence of the condensate is found to decay exponentially in 1D and with a power law in 2D, similarly with the case of conservative systems. The coherence lengths are found to be longer due to the finite life time of the condensate excitations. We compare these properties with the ones of a condensate described by the popular "diffusive" models in which the dissipative term is proportional to the local condensate density. In the latter, the dispersion of excitations is diffusive which as soon as the condensate is put into motion implies finite mechanical friction and can lead to an energetic instability.

cond-mat.quant-gas↗

arXiv2013

Landau versus Spin Superfluidity in Spinor Bose-Einstein Condensates

We consider a spin-1/2 Bose-Einstein condensate prepared initially in a single spin projection. The two channels of excitations existing in such a system (namely density and spin waves) are discussed and we show how pure spin waves can be excited in the presence of local magnetic defects. We analyze the role played by spin excitations on the Landau superfluidity criterion and demonstrate the absence of absolute superfluidity for the antiferromagnetic condensate. In the ferromagnetic case, we identify two critical velocities for the breakdown of superfluidity.

cond-mat.quant-gas↗

arXiv2012

Macroscopic quantum self-trapping and Josephson oscillations of exciton-polaritons

A textbook example of quantum mechanical effects is the coupling of two states through a tunnel barrier. In the case of macroscopic quantum states subject to interactions, the tunnel coupling gives rise to Josephson phenomena including Rabi oscillations, the a.c. and d.c. effects, or macroscopic self-trapping depending on whether tunnelling or interactions dominate. Non-linear Josephson physics, observed in superfluid helium and atomic condensates, has remained inaccessible in photonic systems due to the required effective photon-photon interactions. We report on the observation of non-linear Josephson oscillations of two coupled polariton condensates confined in a photonic molecule etched in a semiconductor microcavity. By varying both the distance between the micropillars forming the molecule and the condensate density in each micropillar, we control the ratio of coupling to interaction energy. At low densities we observe coherent oscillations of particles tunnelling between the two micropillars. At high densities, interactions quench the transfer of particles inducing the macroscopic self-trapping of the condensate in one of the micropillars. The finite lifetime of polaritons results in a dynamical transition from self-trapping to oscillations with pi phase. Our results open the way to the experimental study of highly non-linear regimes in photonic systems, such as chaos or symmetry-breaking bifurcations.

cond-mat.mes-hall↗

arXiv2012

Skyrmion Formation and Optical Spin-Hall Effect in an Expanding Coherent Cloud of Indirect Excitons

We provide a theoretical description of the polarization pattern and phase singularities experimentally evidenced recently in a condensate of indirect excitons [H. High et al., Nature 483, 584-588 (2012)]. We show that the averaging of the electron and hole orbital motion leads to a comparable spin-orbit interaction for both type of carriers. We demonstrate that the interplay between a radial coherent flux of bright indirect excitons and the Dresselhaus spin-orbit interaction results in the formation of spin domains and of topological defects similar to Skyrmions. We reproduce qualitatively all the features of the experimental data and obtain polarization pattern as in the optical spin Hall effect despite the different symmetry of the spin-orbit interactions.

cond-mat.mes-hall↗

arXiv2012

Parametric Inversion of Spin Currents in Semiconductor Microcavities

The optical spin-Hall effect results in the formation of an antisymmetric real space polarization pattern forming spin currents. In this paper, we show that the exciton-polariton parametric scattering allows us to reverse the sign of these currents. We describe the pulsed resonant excitation of a strongly coupled microcavity with a linearly polarized pump at normal incidence. The energy of the pulse is set to be close to the inflexion point of the polariton dispersion and the focusing in real space populates the reciprocal space on a ring. For pumping powers below the parametric scattering threshold, the propagation of the injected polaritons in the effective magnetic field induced by the TE and TM splitting produce the normal optical spin-Hall effect. Keeping the same input polarization but increasing the pump intensity, the parametric scattering towards an idler and a signal state is triggered on the whole elastic circle. The injected particles are scattered toward these states while propagating radially all over the plane, gaining a cross linear polarisation with respect to the pump during the nonlinear process. Eventually, the propagation of the polaritons in the effective field results in the optical spin Hall-effect, but this time with inverted polarization domains.

cond-mat.mes-hall↗

arXiv2012

Propagation and amplification dynamics of 1D polariton condensates

The dynamics of propagating polariton condensates in one-dimensional microcavities is investigated through time resolved experiments. We find a strong increase in the condensate intensity when it travels through the non-resonantly excited area. This amplification is shown to come from bosonic stimulated relaxation of reservoir excitons into the polariton condensate, allowing for the repopulation of the condensate through non-resonant pumping. Thus, we experimentally demonstrate a polariton amplifier with a large band width, opening the way towards the transport of polaritons with high densities over macroscopic distances.

cond-mat.quant-gas↗

arXiv2012

Topological Wigner Crystal of Half-Solitons in a Spinor BEC

We consider a one-dimensional gas of half-solitons in a spinor Bose-Einstein condensate. We calculate the topological interaction potential between the half-solitons. Using a kinetic equation of the Vlasov-Boltzmann type, we model the coupled dynamics of the interacting solitons. We show that the dynamics of the system in the gaseous phase is marginally stable and spontaneously evolves towards a Wigner crystal.

cond-mat.quant-gas↗

arXiv2012

Transmutation from Skyrmions to Half-Solitons Driven by the Nonlinear Optical Spin-Hall Effect

We show that the polarization domains generated in the linear optical spin-Hall effect by the analog of spin-orbit interaction for exciton-polaritons are associated with the formation of a Skyrmion lattice. In the non-linear regime, the spin anisotropy of the polariton-polariton interactions results in a spatial compression of the spin domains and in an abrupt transformation of the Skyrmions into half-solitons, associated with both the focalization of the spin currents and the emergence of a strongly anisotropic emission pattern.

cond-mat.mes-hall↗

arXiv2012

Half-solitons in a polariton quantum fluid behave like magnetic monopoles

Monopoles are magnetic charges, point-like sources of magnetic field. Contrary to electric charges they are absent in Maxwell's equations and have never been observed as fundamental particles. Quantum fluids such as spinor Bose-Einstein condensates have been predicted to show monopoles in the form of excitations combining phase and spin topologies. Thanks to its unique spin structure and the direct optical control of the fluid wavefunction, an ideal system to experimentally explore this phenomenon is a condensate of exciton-polaritons in a semiconductor microcavity. We use this system to create half-solitons, non-linear excitations with mixed spin-phase geometry. By tracking their trajectory, we demonstrate that half-solitons behave as monopoles, magnetic charges accelerated along an effective magnetic field present in the microcavity. The field-induced spatial separation of half-solitons of opposite charges opens the way to the generation of magnetic currents in a quantum fluid.

cond-mat.quant-gas↗

arXiv2011

Multistability of cavity exciton-polaritons affected by the thermally generated exciton reservoir

Until now, the generation of an excitonic reservoir in a cavity polariton system under quasi-resonant pumping has always been neglected. We show that in microcavities having a small Rabi splitting (typically GaAs cavities with a single quantum well), this reservoir can be efficiently populated by polariton-phonon scattering. We consider the influence of the exciton reservoir on the energy shifts of the resonantly pumped polariton modes. We show that the presence of this reservoir effectively reduces the spin anisotropy of the polariton-polariton interaction, in agreement with recent experimental measurements, where the multistability of cavity polaritons has been analyzed

cond-mat.mes-hall↗

arXiv2011

Stable magnetic monopoles in spinor polariton condensates

We consider half-integer topological defects in a spinor Bose-Einstein condensate of exciton-polaritons. We show that they accelerate under the effect of an in-plane effective magnetic field, like regular electric charges in the electric field. The trajectories of these analogues of magnetic monopoles are derived analytically and checked by numerical simulations. We show that these "magnetic charges" propagate at large in-plane velocities and remain stable up to a critical magnetic field, thanks to the unique spin-anisotropy of polariton interactions.

cond-mat.mes-hall↗

arXiv2011

Black Holes and Wormholes in spinor polariton condensates

We propose a new system for the study of event horizons and black holes - a Bose-Einstein condensate of exciton-polaritons. Hawking radiation from a closed horizon in 2D is observed in numerical experiments. We simulate inter-Universe and intra-Universe wormholes capitalizing on the spinor nature of polariton condensates and on the spin dependence of polariton-polariton interactions.

cond-mat.mes-hall↗

arXiv2011

Coherent interactions between phonons and exciton or exciton-polariton condensates

We analyse the interaction of exciton and exciton-polariton condensates in semiconductor microcavity with a coherent acoustic wave. An analytical solution for the dispersion of excitations of coupled condensate-phonon system is found in the approximation of k-independent interactions. Accounting for k-dependence results in a stronger modification of the dispersion, and even in the appearance of the "roton instability" region.

cond-mat.mtrl-sci↗

arXiv2010

Optically and electrically controlled polariton spin transistor

We propose two schemes of a novel spin-optronic device, optical analog of Datta and Das spin transistor for the electrons. The role of ferromagnetic contacts is played by one-dimensional polariton channels with strong TE-TM splitting. A symmetric 2D trap plays a role of the non-magnetic active region. The rotation of the polarization of the pulse in this region can be achieved either due to its interaction with a spatially confined polariton condensate created resonantly by a circular polarized laser, either due to the splitting between the two linear polarizations of the excitons, controlled electrically by use of metallic gate.

cond-mat.mes-hall↗