arXiv subjects

Igor Chestnov

Publications and source records attributed to Igor Chestnov.

10 recordsLinked to original sources

arXiv2025

Non-Hermitian trapping of Dirac exciton-polariton condensates in a perovskite metasurface

Massless Dirac particles avoid trapping due to their exceptional tunneling properties manifested in the so-called Klein paradox. This conclusion stems from the conservative treatment, but so far, it has not been extended to a non-Hermitian framework. Recently, driven-dissipative bosonic condensation of Dirac exciton-polaritons was demonstrated in metasurface waveguides. Here, we report an experimental observation of spatial binding and energy quantization of Dirac exciton-polaritons in a halide perovskite metasurface. A combination of spatially profiled nonresonant optical excitation and exciton-polariton interaction forms an effective non-Hermitian complex potential responsible for the observed effect. In the case of tightly focused pump spots spanning from 9 to 17~$\mu$m, several bound states simultaneously achieve macroscopic occupation, constituting a multi-mode bosonic condensation of exciton-polaritons. Our theoretical analysis based on the driven-dissipative extension of the Dirac equation reveals that the non-Hermitian character of the effective trap allows for confinement even in the case of the gapless Dirac-like photonic dispersion, both above and below the energy of the dispersion crossing.

cond-mat.mes-hall↗

arXiv2025

Deeply Subwavelength Blue-Range Nanolaser

Modern high-definition display and augmented reality technologies require the development of ultracompact micro- and nano-pixels with colors covering the full gamut and high brightness. In this regard, lasing nano-pixels emitting light in the spectral range 400-700 nm are highly demanded. Despite progress in red, green, and ultraviolet nanolasers, the demonstrated blue-range (400-500 nm) single-particle-based lasers are still not subwavelength yet. Here we fabricate CsPbCl$_3$ cubic-shaped single-crystal nanolasers on a silver substrate by wet chemistry synthesis, producing their size range around 100-500 nm, where the nanoparticle with sizes 0.145$\mu$m$\times$0.195$\mu$m$\times$0.19$\mu$m and volume 0.005 $\mu$m$^3$ (i.e. $\sim\lambda^3$/13) is the smallest nanolaser among the lasers operating in the blue range reported so far, with emission wavelength around $\lambda\approx 415$ nm. Experimental results at a temperature of 80 K and theoretical modeling show that the CsPbCl$_3$ nanolaser is a polaritonic laser where exciton-polaritons are strongly coupled with Mie resonances enhanced by the metallic substrate. As a result, the combination of the strong excitonic response of CsPbCl$_3$ materials, its high crystalline quality, and optimized optical resonant properties resulting in a population-inversion-free lasing regime are the key factors making the proposed nanolaser design superior among previously reported ones in the blue spectral range.

physics.optics↗

arXiv2024

Exciton-polariton stimulated scattering in hybrid halide perovskites

Halide perovskites, such as methylammonium lead bromide (MAPbBr$_3$), host tightly bound three-dimensional excitons which are robust at room temperature. Excellent optical properties of MAPbBr$_3$ allow for designing of optical single-mode waveguides and cavities in the frequency range close to the excitonic transitions. Taken together, this turns MAPbBr$_3$ into an excellent platform for probing exciton-polariton nonlinear phenomena at room temperature. Here we investigate ultrafast non-equilibrium dynamics of polaritons under pulsed fs non-resonant excitation. We demonstrate the presence of the stimulated acoustic phonon-assisted scattering regime above threshold pump fluence, characterized by the explosive growth of emission intensity, a redshift of the emission spectral maximum, spectral narrowing, and sub-picosecond emission dynamics. Our theoretical findings are well confirmed by the results of experimental measurements.

cond-mat.mtrl-sci↗

arXiv2023

Symmetry breaking and superfluid currents in a split-ring spinor polariton condensate

Bosonic condensates of spin-less non-interacting particles confined on a ring cannot propagate circular periodic currents once rotation symmetry of the system is broken. However a persistent current may appear due to inter-particle interactions exceeding some critical strength. In this up-critical regime breaking of the symmetry between the clockwise and anticlockwise rotations takes place. We consider this symmetry-breaking scenario in the case of a spinor condensate of exciton polaritons trapped on a ring split by a potential barrier. Due to the intrinsic symmetry of the effective spin-orbit interaction which stems from the linear splitting between transverse-electric and transverse-magnetic microcavity modes, the potential barrier blocks the circulating current and imposes linear polarization patterns. On the other hand, circularly polarized polaritons form circular currents propagating in opposite directions with equal absolute values of angular momentum. In the presence of inter-particle interactions, the symmetry of clockwise and anticlockwise currents can be broken spontaneously. We describe several symmetry-breaking scenarios which imply either restoration of the global condensate rotation or the onset of the circular polarization in the symmetry-broken state.

cond-mat.mes-hall↗

arXiv2022

Light-induced injection of hot carriers from gold nanoparticles to carbon wire bundles

We observed a light-induced enhancement of the tunneling current propagating through an array of parallel carbon chains anchored between gold nanoparticles (NPs). In the presence of laser radiation characterized by a wavelength close to the plasmon resonance of the NPs, the current-voltage characteristics of carbon bundle tunnelling junctions demonstrate a pronounced asymmetry between positive and negative bias values. Such an asymmetry is typical for a Schottky junction, in general. The resistance of the tunnel junction decreases with the increase of the optical pumping intensity. We associate the observed effect with an injection of `hot' carriers created in Au NPs due to the decay of the surface plasmons accompanied by the charge transfer to the carbon bundles. The observed phenomenon can be used for non-resonant excitation of excitonic states in low-dimensional carbon-based structures for single-photon emission, as well as for photovoltaic applications.

cond-mat.mes-hall↗

arXiv2022

Double ring polariton condensates with polariton vortices

We study formation of superfluid currents of exciton polaritons in annular polariton condensates in a cylindrical micropillar cavity under the spatially localised nonresonant optical pumping. Since polariton condensates are strongly nonequilibrium systems, the trapping potential for polaritons, formed by the pillar edge and the reservoir of optically induced incoherent excitons, is complex in general case. Its imaginary part includes the spatially distributed gain from the pump and losses of polaritons in the condensate. We show that engineering the gain-loss balance in the micropillar plane gives access to the excited states of the polariton condensate. We demonstrate both theoretically and experimentally formation of vortices in double concentric ring polariton condensates in the complex annular trap potential.

cond-mat.mes-hall↗

arXiv2022

Spinor superfluid currents of exciton-polaritons on a split-ring

Recently, split-ring bosonic condensates of exciton polaritons have been proposed for realisation of qubits. We formulate an analytical model of a polariton condensate in a one-dimensional ring split by a delta-function potential. The persistent current is stopped by the potential defect embedded in a scalar condensate of non-interacting particles, however, it reappears in the presence of an up-critical non-linearity. The nonlinear supercurrents are characterised by fractional orbital momenta while their eigenfunctions may feature grey or dark solitons. The coupling between the spin and the orbital angular momentum of a spinor condensate affects persistent currents crucially. We show that the spin-orbit interaction (SOI) induces the net superfluid current in the condensate with a spatially uniform spin polarisation. We also find solutions where the SOI-induced currents of two spin components of the condensate propagate in opposite directions. The corresponding states of spinor condensates obey a combined mirror reflection and the spin-flip symmetry.

cond-mat.mes-hall↗

arXiv2019

Electric field assisted alignment of monoatomic carbon chains

We stabilize monoatomic carbon chains in water by attaching them to gold nanoparticles (NPs) by means of the laser ablation process. Resulting nanoobjects represent pairs of NPs connected by multiple straight carbon chains of several nanometer lengths. If NPs at the opposite ends of a chain differ in size, the structure acquires a dipole moment due to the difference in work functions of the two NPs. We take advantage of the dipole polarisation of carbon chains for ordering them by the external electric field. We deposit them on a glass substrate by the sputtering method in the presence of static electric fields of magnitudes up to 10^5 V/m. The formation of one-dimensional carbyne quasi-crystals deposited on a substrate is evidenced by high-resolution TEM and X-ray diffraction measurements. The original kinetic model describing the dynamics of ballistically flowing nano-dipoles reproduces the experimental diagram of orientation of the deposited chains.

physics.atm-clus↗

arXiv2019

Split-ring polariton condensates as macroscopic two-level quantum systems

Superposition states of circular currents of exciton-polaritons mimic the superconducting flux qubits. The phase of a polariton fluid must change by an integer number of $2\pi$, when going around the ring. If one introduces a ${\pi}$-phase delay line in the ring, the fluid is obliged to propagate a clockwise or anticlockwise circular current to reduce the total phase gained over one round-trip to zero or to build it up to $2\pi$. We show that such a $\pi$-delay line can be provided by a dark soliton pinned to a potential well created by a C-shape non-resonant pump-spot. The resulting split-ring polariton condensates exhibit pronounced coherent oscillations passing periodically through clockwise and anticlockwise current states. These oscillations may persist far beyond the coherence time of polariton condensates. The qubits based on split-ring polariton condensates are expected to possess very high figures of merit that makes them a valuable alternative to superconducting qubits. The use of the dipole-polarized polaritons allows to control coherently the state of the qubit with the external electric field. This is shown to be one of the tools for realization of single-qubit logic operations. We propose the design of an $i$SWAP gate based on a pair of coupled polariton qubits. To demonstrate the capacity of the polariton platform for quantum computations, we propose a protocol for the realization of the Deutsch's algorithm with polariton qubit networks.

cond-mat.mes-hall↗

arXiv2018

Self-trapping of exciton-polariton condensates

The self-trapping of exciton-polariton condensates is demonstrated and explained by the formation of a new polaron-like state. Above the polariton lasing threshold, local variation of the lattice temperature provides the mechanism for an attractive interaction between polaritons. Due to this attraction, the condensate collapses into a small bright spot. Its position and momentum variances approach the Heisenberg quantum limit. The self-trapping does not require either a resonant driving force or a presence of defects. The trapped state is stabilized by the phonon-assisted stimulated scattering of excitons into the polariton condensate. While the formation mechanism of the observed self-trapped state is similar to the Landau-Pekar polaron model, this state is populated by several thousands of quasiparticles, in a strike contrast to the conventional single-particle polaron state.

cond-mat.quant-gas↗