arXiv subjects

I. Yu. Chestnov

Publications and source records attributed to I. Yu. Chestnov.

14 recordsLinked to original sources

arXiv2026

Room-temperature local strain control of moir\'e excitons in MoS$_2$/WSe$_2$ heterobilayers

Moir\'e superlattices in heterobilayers of atomically thin transition metal dichalcogenides provide a versatile platform for exploring quantum many-body physics as they can trap excitons, leading to the formation of quantized moir\'e exciton states. However, such moir\'e excitons have been predominantly studied at cryogenic temperatures, which severely limits their practical applications. Here, we demonstrate room-temperature activation and control of moir\'e excitons in MoS$_2$/WSe$_2$ heterobilayers using local strain engineering. Applying mechanical strain with a modified atomic force microscopy tip, we observe a series of resonances attributed to interlayer exciton states confined in the moir\'e potential. Power-dependent photoluminescence measurements elucidate the population dynamics of the moir\'e exciton states, while controlled local strain enables continuous tuning of their emission wavelength to the center of the second telecom window. We provide a theoretical model that captures all experimentally observed features, including the unconventional spectral shape of the moir\'e exciton emission. Our findings establish local tip-induced strain as a powerful tool for the on-demand manipulation of moir\'e excitons, paving the way for room-temperature quantum excitonic devices.

cond-mat.mes-hall↗

arXiv2026

Josephson and Spin Currents in Coupled Polariton Condensates

We analyze particle and spin currents in networks of coupled spinor exciton-polariton condensates arranged as plaquettes and regular polygonal rings. In closed geometries, spin-conserving and TE-TM-induced spin-flip tunnelling combine to generate circulating particle currents, hidden spin counterflows, and bond-dependent spin-current patterns. For the minimal geometries - an equilateral triangle, and a square plaquette - we derive analytical expressions for edge-resolved currents from stationary configurations obtained by energy minimization. We then show how particle, in-plane spin, and out-of-plane spin currents partition the parameter plane and provide direct signatures of the equilibrium phases. Finally, we apply the same current-resolved diagnostics to larger rings, where winding numbers and a branch-invariant common-phase coherence metric organize the resulting phase structure.

cond-mat.mes-hall↗

arXiv2025

Supersolidity in Optically Trapped Polariton Condensates

Superfluids under specific conditions can exhibit spontaneous breaking of continuous translation symmetries and form exotic spatially ordered states of matter known as supersolids. Despite its early theoretical prediction, it took over half-a-centrury to experimentally demonstrate the supersolid phase in ultracold atomic Bose-Einstein condensates, forming due to long-range interatomic interactions. Here we propose as a promising new platform for supersolidity exciton-polariton superfluids, confined in annular optically induced traps. The supersolid phase emerges due to effective attractive interactions, mediated by the normal excitonic component of the system. Experimental demonstration of spontaneously formed spatially ordered phase is in agreement with detailed mean-field theoretical analysis and numerical simulation. The spontaneous character of the observed supersolid transition is further evidenced by the formation of specific zero-energy Nambu-Goldstone modes in the collective excitation spectrum.

cond-mat.mes-hall↗

arXiv2025

Spin-Meissner effect in systems of coupled polariton condensates

We theoretically investigate the interplay between Zeeman splitting and TE-TM-induced spin-flip tunneling in coupled exciton-polariton condensates systems and its impact on the spin-Meissner effect. We demonstrate that although a single condensate exhibits the effect of full paramagnetic screening via spin-anisotropic interactions, the inter-site spin-flip tunneling can dramatically alter this behavior. The geometry of the system is shown to play a crucial role. In particular, in a dyad, the chemical potential reveals quadratic scaling with the magnetic field. In a triangle, the competition between Zeeman and TE-TM splittings produces a rich phase diagram that features asymmetric polarization states corresponding to both positive and negative magnetic susceptibility. In a square configuration, the symmetry of the network can restore the spin-Meissner effect, so that the condensate emission frequency becomes magnetic field independent in an extended parameter range. These findings not only shed light on the fundamental physics of polariton lattices but also suggest promising avenues for engineering robust spin-controlled photonic devices and polaritonic simulators.

cond-mat.mes-hall↗

arXiv2024

Non-classical effects in polariton trion

We investigate quantum phenomena in a system of three coupled microcavities. The possibility of observing polariton blockade in a dimer and triple micropillar configuration is discussed. The discovered quantum effects allow using these systems as versatile sources of individual polariton photons. Various manifestations of the quantum blockade can be tuned with the use of the pumping laser frequency. We discovered that the action of an artificial gauge field on a polariton trion causes the effect of a collective quantum blockade -- a phenomenon consisting in blocking of excitation of the state with $n$ particles distributed over multiple coupled modes. We found that when a collective quantum blockade on a non-Hermitain polariton dimer as part of the trion and a blockade on the machine itself with an antibunching effect of a micropillar coupled to the dimer, then a polariton dimer is entangled with that micropillar.

cond-mat.mes-hall↗

arXiv2020

Spin noise signatures of the self-induced Larmor precession

Bose-Einstein condensates of exciton-polaritons are known for their fascinating coherent and polarization properties. The spin state of the condensate is reflected in polarization of the exciton-polariton emission, with temporal fluctuations of this polarization being, in general, capable of reflecting quantum statistics of polaritons in the condensate. To study the polarization properties of optically trapped polariton condensates, we take advantage of the spin noise spectroscopy technique. The ratio between the noise of ellipticity of the condensate emission and its polarization plane rotation noise is found to be dependent, in a nontrivial way, on the intensity of CW nonresonant laser pumping. We show that the interplay between the ellipticity and the rotation noise can be explained in terms of the competition between the self-induced Larmor precession of the condensate pseudospin and the static polarization anisotropy of the microcavity.

cond-mat.mes-hall↗

arXiv2018

Heat-assisted self-localization of exciton polaritons

Bosonic condensation of microcavity polaritons is accompanied by their relaxation from the ensemble of excited states into a single quantum state. The excess of energy is transferred to the crystal lattice that eventually involves heating of the structure. Creation of the condensate results in the local increase of the temperature which leads to the red shift of the exciton energy providing the mechanism for polariton self-trapping. By employing the driven-dissipative Gross-Pitaevskii model we predict a new type of a stable localized solution supported by the thermally-induced self-trapping in a one-dimensional microcavity structure. The predicted solution is of a sink-type i.e. it is characterized by the presence of converging density currents. We examine the spontaneous formation of these states from the white noise under spatially localized pumping and analyze the criteria for their stability. The collective bosonic polaron state described here may be considered as a toy model for studies of bosonic stars formed due to the self-gravity effect.

cond-mat.mes-hall↗

arXiv2016

Nonlinear Bloch-waves and current states of exciton-polariton condensates

The formation of nonlinear Bloch states in open driven-dissipative system of exciton-polaritons loaded into a weak-contrast 1D periodic lattice is studied numerically and analytically. The condensate is described within the framework of mean-field theory by the coupled equations for the order parameter and for the density of incoherent excitons. The stationary nonlinear solutions having the structure of Bloch waves are studied in detail. It is shown that there is a bifurcation leading to the appearance of a family of essentially nonlinear states. The special feature of these solutions is that its current does not vanish when the quasi-momentum of the state approaches the values equal to the half of the lattice constant. To explain the bifurcations found in numerical simulations a simple perturbative approach is developed. The stability of the nonlinear states is examined by linear spectral analysis and by direct numerical simulations. An experimental scheme allowing the observation of the discussed nonlinear current states is suggested and studied by numerical simulations.

cond-mat.mes-hall↗

arXiv2015

Oscillatory dynamics of non-equilibrium dissipative exciton-polariton condensates in weak-contrast lattices

We study nonlinear dynamics of exciton-polaritons in an incoherently pumped semiconductor microcavity with embedded weak-contrast lattice and coupled to an exciton reservoir. We elucidate fundamental features of non-equilibrium exciton-polariton condensate trapped in one-dimensional periodical potential close to zero momentum (so-called "Zero-state") and to the state at the boundary of Brillouin zone ("$π$-state"). Within the framework of the mean-field theory, we identify different regimes of both relaxation and oscillatory dynamics of coherent exciton-polaritons governed by superpositions of Bloch eigenstates within the periodic lattice. In particular, we theoretically demonstrate stable macroscopical oscillations, akin to nonlinear Josephson oscillations, between different spectral components of a polariton condensate in the momenta-space. We elucidate a strong influence of the dissipative effects and the feedback induced by the inhomogeneity of incoherent reservoir on the dynamics of the coherent polaritons.

cond-mat.mes-hall↗

arXiv2014

Qubits based on Polariton Rabi Oscillators

We propose a novel physical mechanism for creation of long lived macroscopic exciton-photon qubits in semiconductor microcavities with embedded quantum wells in the strong couping regime. We argue that the coherence time of Rabi oscillations can be dramatically enhanced due to their stimulated pumping from a permanent thermal reservoir of polaritons. The polariton qubit is a superposition of lower branch (LP) and upper branch (UP) exciton-polariton states. We discuss applications of such qubits for quantum information processing, cloning and storage purposes.

cond-mat.mes-hall↗

arXiv2013

Lasing and high temperature phase transitions in atomic systems with dressed state polaritons

We consider the fundamental problem of high temperature phase transitions in the system of high density two-level atoms off-resonantly interacting with a pump field in the presence of optical collisions (OCs) and placed in the cavity. OCs are considered in the framework of thermalization of atomic dressed state (DS) population. For the case of a strong atom-field coupling condition we analyze the problem of thermodynamically equilibrium superradiant phase transition for the order parameter representing a real amplitude of cavity mode and taking place as a result of atomic DSs thermalization process. Such transition is also connected with condensed (coherent) properties of low branch (LB) DS-polaritons occurring in the cavity. For describing non-equilibrium phase transitions we derive Maxwell-Bloch like equations which account for cavity decay rate, collisional decay rate and spontaneous emission. Various aspects of transitions to laser field formation by using atomic DS levels for both positive and negative detuning of a pump field from atomic transition frequency are studied in detail. It is revealed, that for positive atom-light detuning DS lasing can be obtained in the presence of quasi-equilibrium DS population that corresponds to a true two-level atomic system with the inversion in nonresonant limit.

quant-ph↗

arXiv2012

Bose-Einstein condensation for trapped atomic polaritons in a biconical waveguide cavity

We study the problem of high temperature Bose-Einstein condensation (BEC) of atom-light polaritons in a waveguide cavity appearing due to interaction of two-level atoms with (non-resonant) quantized optical radiation, in the strong coupling regime, in the presence of optical collisions (OCs) with buffer gas particles. Specifically, we propose a special biconical waveguide cavity (BWC), permitting localization and trapping of low branch (LB) polaritons imposed by the variation of the waveguide radius in longitudinal direction. We have shown that critical temperature of BEC occurring in the system can be high enough -- few hundred Kelvins; it is connected with photon-like character of LB polaritons and strongly depends on waveguide cavity parameters. In the case of a linear trapping potential we obtain an Airy-shaped polariton condensate wave function which, when disturbed out of equilibrium, exhibits small amplitude oscillations with the characteristic period in the picosecond domain.

cond-mat.quant-gas↗

arXiv2011

High temperature phase transition in the coupled atom-light system in the presence of optical collisions

The problem of photonic phase transition for the system of a two-level atomic ensemble interacting with a quantized single-mode electromagnetic field in the presence of optical collisions (OC) is considered. We have shown that for large and negative atom-field detuning a photonic field exhibits high temperature second order phase transition to superradiant state under thermalization condition for coupled atom-light states. Such a transition can be connected with superfluid (coherent) properties of photon-like low branch (LB) polaritons. We discuss the application of metallic cylindrical waveguide for observing predicted effects.

cond-mat.mes-hall↗

arXiv2010

Thermalization of coupled atom-light states in the presence of optical collisions

The interaction of a two-level atomic ensemble with a quantized single mode electromagnetic field in the presence of optical collisions (OC) is investigated both theoretically and experimentally. The main accent is made on achieving thermal equilibrium for coupled atom-light states (in particular dressed states). We propose a model of atomic dressed state thermalization that accounts for the evolution of the pseudo-spin Bloch vector components and characterize the essential role of the spontaneous emission rate in the thermalization process. Our model shows that the time of thermalization of the coupled atom-light states strictly depends on the ratio of the detuning and the resonant Rabi frequency. The predicted time of thermalization is in the nanosecond domain and about ten times shorter than the natural lifetime at full optical power in our experiment. Experimentally we are investigating the interaction of the optical field with rubidium atoms in an ultra-high pressure buffer gas cell under the condition of large atom-field detuning comparable to the thermal energy in frequency units. In particular, an observed detuning dependence of the saturated lineshape is interpreted as evidence for thermal equilibrium of coupled atom-light states. A significant modification of sideband intensity weights is predicted and obtained in this case as well.

cond-mat.mes-hall↗