arXiv subjects

I. G. Savenko

Publications and source records attributed to I. G. Savenko.

At least 55 records · Page 3Linked to original sources

arXiv2018

Excitation of localized condensates in the flat band of exciton-polariton Lieb lattice

We propose a way to directly excite compact localized condensates in a nearly flat band of the exciton-polariton Lieb lattice by short Laguerre-Gaussian pulses and investigate the dynamics of these condensates in the presence of repulsive polariton-polariton interaction and distributed losses in the lattice. The evolution of a low-density compact polariton condensate shows fast Rabi oscillations between its excitonic and photonic components, with slow beatings of the Rabi oscillation amplitude. Both oscillations and beatings are suppressed at higher condensate densities due to polariton-polariton repulsion and distributed losses in the lattice. A background incoherent pumping can be used to increase the lifetime and stability of compact localized states

cond-mat.mes-hall↗

arXiv2018

Reconstruction of Exciton-Polariton Condensates in 1D Periodic Structures

We demonstrate the reconstruction of the exciton-polariton condensate loaded in a single active miniband in one-dimensional microcavity wires with a complex-valued periodic potentials. The effect appears due to strong polariton-polariton repulsion and it depends on the type of the single-particle dispersion of the miniband, which can be fine tuned by the real and imaginary components of the potential. As a result, the condensate can be formed in a $0$-state, $π$-state, or mixed state of spatiotemporal intermittency, depending on the shape of the miniband, strength of interparticle interaction, and distribution of losses in the system. The reconstruction of the condensate wave function takes place by proliferation of nuclei of the new condensate phase in the form of dark solitons. We show that, in general, the interacting polaritons are not condensed in the state with minimal losses, neither they accumulate in the state with a well-defined wave vector.

cond-mat.mes-hall↗

arXiv2018

Evolution of temporal coherence in confined polariton condensates

We study the influence of spatial confinement on the second-order temporal coherence of the emission from a semiconductor microcavity in the strong coupling regime. The confinement, provided by etched micropillars, has a favorable impact on the temporal coherence of solid state quasi-condensates that evolve in our device above threshold. By fitting the experimental data with a microscopic quantum theory based on a quantum jump approach, we scrutinize the influence of pump power and confinement and find that phonon-mediated transitions are enhanced in the case of a confined structure, in which the modes split into a discrete set. By increasing the pump power beyond the condensation threshold, temporal coherence significantly improves in devices with increased spatial confinement, as revealed in the transition from thermal to coherent statistics of the emitted light.

cond-mat.quant-gas↗

arXiv2018

Shedding light on topological superconductors

We propose an optical approach to monitor superconductors in conjunction with a normal metal layer. Effectively such a hybrid system represents a resonator, where electrons are strongly coupled with light. We show that the interaction of light with the superconductor turns out strongly boosted in the presence of the neighboring metal and as a result, the electromagnetic power absorption of the system is dramatically enhanced. It manifests itself in a giant Fanolike resonance which can uniquely characterize the elementary excitations of the system. Our approach is especially promising for topological superconductors, where the Majorana fermions can be revealed and controlled by light.

cond-mat.supr-con↗

arXiv2018

Magnetoplasmon Fano resonance in Bose-Fermi mixtures

We investigate theoretically the magnetoplasmon (cyclotron) resonance in a hybrid system consisting of spatially separated two-dimensional layers of electron and dipolar exciton gases coupled via the Coulomb forces. We study the dynamics of this system under the action of weak alternating external electromagnetic field in the presence of uniform magnetic field, perpendicular to the layers. We reveal that the electromagnetic power absorption exhibits a double-resonance spectrum. We show that the first resonance is associated with the conventional well-studied magnetoplasmon excitations of the electron gas and it has a standard Lorentzian shape, whereas the second resonance is a peculiarity attributed to the Bose-condensed exciton gas. Further, we explicitly demonstrate that the spectrum of the system exhibits an asymmetric Fano-type profile, where the excitonic peak is extremely narrow in comparison with the magnetoplasmon one. We show that the shape of the resonance and the position of the peaks depends on the magnitude of the applied magnetic field, exciton condensate density and exciton-impurity scattering time. In particular, the Fano profile turns into a Lorentzian shape with decreasing exciton-impurity scattering time and the position of the plasmon-associated resonance is mainly sensitive and determined by the magnetic field strength, whereas the exciton-condensate peak position is determined by exciton condensate density. It opens the experimental possibility to determine the latter quantity in cyclotron resonance experiment.

cond-mat.mes-hall↗

arXiv2018

Bogolon-mediated electron capture by impurities in hybrid Bose-Fermi systems

We investigate the processes of electron capture by a Coulomb impurity center residing in a hybrid system consisting of spatially separated two-dimensional layers of electron and Bose-condensed dipolar exciton gases coupled via the Coulomb forces. We calculate the probability of the electron capture accompanied by the emission of a single Bogoliubov excitation (bogolon), similar to regular phonon-mediated scattering in solids. Further, we study the electron capture mediated by the emission of a pair of bogolons in a single capture event and show that these processes not only should be treated in the same order of the perturbation theory, but also they give more important contribution than single bogolon-mediated capture, in contrast with regular phonon scattering.

cond-mat.mes-hall↗

arXiv2018

Phonon-Mediated Phase Transitions in Two-Dimensional Driven-Dissipative Systems

We develop a two-dimensional stochastic dissipative theory for the description of the transport of exciton polaritons accounting for their interaction with the environment of acoustic phonons. Our approach is based on the explicit modeling of the corresponding microscopic processes using a Monte Carlo framework rather than modeling from phenomenological principles. We show the dynamic formation of a condensate and investigate its characteristics, including threshold-like behavior in populations and the formation of spatial and temporal coherence at different temperatures of the environment and accounting for the stimulated nonlinear scattering, caused by system-environment interaction. The spatial coherence reveals a transition from an exponential to polynomial decay which can be attributed to the Berezinskii-Kosterlitzh-Thouless-like phase.

cond-mat.mes-hall↗

arXiv2018

Radiation Pressure Quantization

Kepler's observation of comets tails initiated the research on the radiation pressure of celestial objects and 250 years later they found new incarnation after the Maxwell's equations were formulated to describe a plethora of light-matter coupling phenomena. Further, quantum mechanics gave birth to the photon drag effect. Here, we predict a novel universal phenomenon which can be referred to as quantization of the radiation pressure. We develop a microscopic theory of this effect which can be applied to a general system containing Bose-Einstein-condensed particles, which possess an internal structure of quantum states. By analyzing the response of the system to an external electromagnetic field we find that such drag results in a flux of particles constituting both the condensate and the excited states. We show that in the presence of the condensed phase, the response of the system becomes quantized which manifests itself in a step-like behavior of the particle flux as a function of electromagnetic field frequency with the elementary quantum determined by the internal energy structure of the particles.

cond-mat.mes-hall↗

arXiv2017

Kinetic Monte Carlo Approach to Non-equilibrium Bosonic Systems

We consider the use of a Kinetic Monte Carlo approach for the description of non-equilibrium bosonic systems, taking non-resonantly excited exciton-polariton condensates and bosonic cascade lasers as examples. In the former case, the considered approach allows the study of the cross-over between incoherent and coherent regimes, which represents the formation of a quasi-condensate that forms purely from the action of energy relaxation processes rather than interactions between the condensing particles themselves. In the latter case, we show that a bosonic cascade can theoretically develop an output coherent state.

cond-mat.mes-hall↗

arXiv2017

Paramagnetic resonance in spin-polarized disordered Bose-Einstein condensates

We study the pseudo-spin density response of a disordered two-dimensional spin-polarized Bose gas of exciton polaritons to weak alternating magnetic field, assuming that one of the spin states of the doublet is macroscopically occupied and Bose-condensed while the occupation of the other state remains much smaller. We calculate spatial and temporal dispersions of spin susceptibility of the gas taking into account spin-flip processes due to the transverse-longitudinal splitting. Further, we use the Bogoliubov theory of weakly-interacting gases and show that the time-dependent magnetic field power absorption exhibits double resonance structure corresponding to two particle spin states (contrast to paramagnetic resonance in regular spin-polarized electron gas). We analyze the widths of these resonances caused by scattering on the disorder and show that, in contrast with the ballistic regime, in the presence of impurities, the polariton scattering on them is twofold: scattering on the impurity potential directly and scattering on the spatially fluctuating condensate density caused by the disorder. As a result, the width of the resonance associated with the Bose-condensed spin state can be surprizingly narrow in comparison with the width of the resonance associated with the non-condensed state.

cond-mat.mes-hall↗

arXiv2017

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.

cond-mat.mes-hall↗

arXiv2017

Polariton condensation in photonic crystals with high molecular orientation

We study Frenkel exciton-polariton Bose-Einstein condensation in a two-dimensional defect-free triangular photonic crystal with an organic semiconductor active medium containing bound excitons with dipole moments oriented perpendicular to the layers. We find photonic Bloch modes of the structure and consider their strong coupling regime with the excitonic component. Using the Gross- Pitaevskii equation for exciton polaritons and the Boltzmann equation for the external exciton reservoir, we demonstrate the formation of condensate at the points in reciprocal space where photon group velocity equals zero. Further, we demonstrate condensation at non-zero momentum states for TM-polarized photons in the case of a system with incoherent pumping, and show that the condensation threshold varies for different points in the reciprocal space, controlled by detuning.

physics.optics↗

arXiv2016

Ultrafast exciton-polariton scattering towards the Dirac points

Using the Feynman-Dyson diagram technique, we study nonlinear polariton-polariton scattering in a two-dimensional micropillar-based optical superlattice with hexagonal symmetry. We demonstrate that both the emerging polariton chirality and the loop Feynman diagrams up to infinite order should be strictly accounted for in the evaluation of the self-energy of the system. Further, we explicitly show that in such a design the time of polariton scattering towards the Dirac points can be drastically decreased which can be used, for instance, in engineering novel classes of polariton lasers with substantially reduced thresholds.

cond-mat.mes-hall↗

arXiv2015

Parity measurement of remote qubits using dispersive coupling and photodetection

Parity measurement is a key step in many entanglement generation and quantum error correction schemes. We propose a protocol for non-destructive parity measurement of two remote qubits, i.e., macroscopically separated qubits with no direct interaction. The qubits are instead dispersively coupled to separate resonators that radiate to shared photodetectors. The scheme is deterministic in the sense that there is no fundamental bound on the success probability. Compared to previous proposals, our protocol addresses the scenario where number resolving photodetectors are available but the qubit-resonator coupling is time-independent and only dispersive.

quant-ph↗

arXiv2015

Collective state transitions of exciton-polaritons loaded into a periodic potential

We study the loading of a nonequilibrium, dissipative system of composite bosons -- exciton polaritons -- into a one dimensional periodic lattice potential. Utilizing momentum resolved photoluminescence spectroscopy, we observe a transition between an incoherent Bose gas and a polariton condensate, which undergoes further transitions between different energy states in the band-gap spectrum of the periodic potential with increasing pumping power. We demonstrate controlled loading into distinct energy bands by modifying the size and shape of the excitation beam. The observed effects are comprehensively described in the framework of a nonequilibrium model of polariton condensation. In particular, we implement a stochastic treatment of quantum and thermal fluctuations in the system and confirm that polariton-phonon scattering is a key energy relaxation mechanism enabling transitions from the highly nonequilibrium polariton condensate in the gap to the ground band condensation for large pump powers.

cond-mat.mes-hall↗

arXiv2015

Dissipative soliton protocols in semiconductor microcavities at finite temperatures

We consider exciton polaritons in a semiconductor microcavity with a saturable absorber in the growth direction of the heterostructure. This feature promotes additional nonlinear losses of the system with the emergence of bistability of the condensate particles number on the nonresonant (electrical or optical) excitation intensity. Further we demonstrate a new type of bright spatial dissipative exciton-polariton soliton which emerges in the equilibrium between the regions with different particle density. We develop protocols of soliton creation and destruction. The switch to a soliton-like behavior occurs if the cavity is exposed by a short strong laser pulse with certain energy and duration. We estimate the characteristic times of soliton switch on and off and the time of return to the initial cycle. In particular, we demonstrate surprising narrowing of the spatial profile of the soliton and its vanishing at certain temperature due to interaction of the system with the thermal bath of acoustic phonons. We also address the role of polariton-polariton interaction (Kerr-like nonlinearity) on formation of dissipative solitons and show that the soliton may exist both in its presence and absence.

cond-mat.mes-hall↗

arXiv2015

Quantum Treatment for Bose-Einstein Condensation in Non-Equilibrium Systems

We develop an approach based on stochastic quantum trajectories for an incoherently pumped system of interacting bosons relaxing their energy in a thermal reservoir. Our approach enables the study of the versatile coherence properties of the system. We apply the model to exciton polaritons in a semiconductor microcavity. Our results demonstrate the onset of macroscopic occupation in the lowest-energy mode accompanied by the establishment of both temporal and spatial coherence. We show that temporal coherence exhibits a transition from a thermal to coherent statistics and the spatial coherence reveals off-diagonal long-range order.

cond-mat.quant-gas↗

arXiv2015

Fluctuations of work in nearly adiabatically driven open quantum systems

We extend the quantum jump method to nearly adiabatically driven open quantum systems in a way that allows for an accurate account of the external driving in the system-environment interaction. Using this framework, we construct the corresponding trajectory-dependent work performed on the system and derive the integral fluctuation theorem and the Jarzynski equality for nearly adiabatic driving. We show that such identities hold as long as the stochastic dynamics and work variable are consistently defined. We numerically study the emerging work statistics for a two-level quantum system and find that the conventional diabatic approximation is unable to capture some prominent features arising from driving such as the continuity of the probability density of work. Our results reveal the necessity of using accurate expressions for the drive-dressed heat exchange in future experiments probing jump time distributions.

quant-ph↗