Exciton-polariton Condensates Research Articles

Beyond mean-field corrections to the blueshift of a driven-dissipative exciton-polariton condensate

Beyond mean-field corrections to the blueshift of a driven-dissipative exciton-polariton condensate

Soliton formation in an exciton-polariton condensate at a bound state in the continuum

Soliton formation in an exciton-polariton condensate at a bound state in the continuum

Topological excitation of exciton-polariton half-vortices and skyrmions in a magnetic field with TE-TM splitting

We explore the topological generation of skyrmions and half-vortices in a uniform spinor exciton-polariton condensate featuring TE-TM splitting and exposed to an external magnetic field. The manipulation of pump intensity and magnetic field enables precise control over the spin texture and integrated winding number. Specifically, under an excitation condition where the power applied to the vortex state surpasses that on the non-vortex state by an amount dictated by the magnetic field, skyrmions emerge. These skyrmions exhibit a distinctive spin texture characterized by a circular polarization inversion extending from the center to the periphery. Conversely, reversing the excitation condition, where the power on the vortex state is diminished with the reversal of the magnetic field direction, leads to the creation of half-vortices across the entire condensate, devoid of any circular polarization inversion. In additional to the skyrmions and half-vortices, half-skyrmions can be also generated in the same configuration without magnetic field.

Modulational instability mechanisms in exciton-polariton condensates

Modulational instability mechanisms in exciton-polariton condensates

Optical spin hall effect in exciton-polariton condensates in lead halide perovskite microcavities.

An exciton-polariton condensate is a hybrid light-matter state in the quantum fluid phase. The photonic component endows it with characters of spin, as represented by circular polarization. Spin-polarization can form stochastically for quasi-equilibrium exciton-polariton condensates at parallel momentum vector k|| ∼ 0 from bifurcation or deterministically for propagating condensates at k|| > 0 from the optical spin-Hall effect (OSHE). Here, we report deterministic spin-polarization in exciton-polariton condensates at k|| ∼ 0 in microcavities containing methylammonium lead bromide perovskite (CH3NH3PbBr3) single crystals under non-resonant and linearly polarized excitation. We observe two energetically split condensates with opposite circular polarizations and attribute this observation to the presence of strong birefringence, which introduces a large OSHE at k|| ∼ 0 and pins the condensates in a particular spin state. Such spin-polarized exciton-polariton condensates may serve not only as circularly polarized laser sources but also as effective alternatives to ultracold atom Bose-Einstein condensates in quantum simulators of many-body spin-orbit coupling processes.

Exciton polariton condensation from bound states in the continuum at room temperature

Exciton–polaritons (polaritons) resulting from the strong exciton–photon interaction stimulates the development of novel low-threshold coherent light sources to circumvent the ever-increasing energy demands of optical communications1–3. Polaritons from bound states in the continuum (BICs) are promising for Bose–Einstein condensation owing to their theoretically infinite quality factors, which provide prolonged lifetimes and benefit the polariton accumulations4–7. However, BIC polariton condensation remains limited to cryogenic temperatures ascribed to the small exciton binding energies of conventional material platforms. Herein, we demonstrated room-temperature BIC polariton condensation in perovskite photonic crystal lattices. BIC polariton condensation was demonstrated at the vicinity of the saddle point of polariton dispersion that generates directional vortex beam emission with long-range coherence. We also explore the peculiar switching effect among the miniaturized BIC polariton modes through effective polariton−polariton scattering. Our work paves the way for the practical implementation of BIC polariton condensates for integrated photonic and topological circuits.

Selective Excitation of Exciton-Polariton Condensate Modes in an Annular Perovskite Microcavity.

Exciton-polariton systems composed of a light-matter quasi-particle with a light effective mass easily realize Bose-Einstein condensation. In this work, we constructed an annular trap in a halide perovskite semiconductor microcavity and observed the spontaneous formation of symmetrical petal-shaped exciton-polariton condensation in the annular trap at room temperature. In our study, we found that the number of petals of the petal-shaped exciton-polariton condensates, which is decided by the orbital angular momentum, is dependent on the light intensity distribution. Therefore, the selective excitation of perovskite microcavity exciton-polariton condensates under all-optical control can be realized by adjusting the light intensity distribution. This could pave the way to room-temperature topological devices, optical cryptographical devices, and new quantum gyroscopes in the exciton-polariton system.

Direct Writing of Room Temperature Polariton Condensate Lattice.

Realizing lattices of exciton polariton condensates has been of much interest owing to the potential of such systems to realize analogue Hamiltonian simulators and physical computing architectures. Here, we report the realization of a room temperature polariton condensate lattice using a direct-write approach. Polariton condensation is achieved in a microcavity embedded with host-guest Frenkel excitons of an organic dye (rhodamine) in a small-molecule ionic isolation lattice (SMILES). The microcavity is patterned using focused ion beam etching to realize arbitrary lattice geometries, including defect sites on demand. The band structure of the lattice and the emergence of condensation are imaged using momentum-resolved spectroscopy. The introduction of defect sites is shown to lower the condensation threshold and result in the formation of a defect band in the condensation spectrum. The present approach allows us to study periodic, quasiperiodic, and disordered polariton condensate lattices at room temperature using a direct-write approach.

Nonequilibrium spinor exciton-polariton condensates in a magnetic field

A complete-nonequilibrium model is proposed to investigate spinor exciton-polariton condensates (SEPCs) in a magnetic field. Due to the Zeeman splitting (ZS), the loss rates of two spin components in a magnetic field are distinct and affected by the magnetic field. Therefore, the individual spin component of a SEPC has its own threshold pump power. We investigate the ZS and degree of circular polarization of the SEPC as a function of the excitation power and magnetic field. Above both spin-dependent threshold pump powers, we find an increasing degree of circular polarization with the magnetic field and a quenching of the ZS below a critical strength of the magnetic field. The ZS of a SEPC shows a reverse sign and its magnitude is increasing significantly compared to the uncondensed exciton-polartion ZS. The effect of a magnetic field on excitation spectra of SEPCs are also investigated. We find that the excitation dispersions are Bogoliubov excitations if the pump power is low. The nonequilibrium fluctuations in a SEPC are reduced when a magnetic field is applied.

Dirac exciton–polariton condensates in photonic crystal gratings

Abstract Bound states in the continuum have recently been utilized in photonic crystal gratings to achieve strong coupling and ultralow threshold condensation of exciton–polariton quasiparticles with atypical Dirac-like features in their dispersion relation. Here, we develop the single- and many-body theory of these new effective relativistic polaritonic modes and describe their mean-field condensation dynamics facilitated by the interplay between protection from the radiative continuum and negative-mass optical trapping. Our theory accounts for tunable grating parameters giving full control over the diffractive coupling properties between guided polaritons and the radiative continuum, unexplored for polariton condensates. In particular, we discover stable cyclical condensate solutions mimicking a driven-dissipative analog of the zitterbewegung effect characterized by coherent superposition of ballistic and trapped polariton waves. We clarify important distinctions between the polariton nearfield and farfield explaining recent experiments on the emission characteristics of these long lived nonlinear Dirac polaritons.

Qubit gate operations in elliptically trapped polariton condensates

We consider bosonic condensates of exciton-polaritons optically confined in elliptical traps. A superposition of two non-degenerated p-type states of the condensate oriented along the two main axes of the trap is represented by a point on a Bloch sphere, being considered as an optically tunable qubit. We describe a set of universal single-qubit gates resulting in a controllable shift of the Bloch vector by means of an auxiliary laser beam. Moreover, we consider interaction mechanisms between two neighboring traps that enable designing two-qubit operations such as CPHASE and CNOT gates. Both the single- and two-qubit gates are analyzed in the presence of error sources in the context of polariton traps, such as pure dephasing and spontaneous relaxation mechanisms, leading to a fidelity reduction of the final qubit states and quantum concurrence, as well as the increase of Von Neumann entropy. We also discuss the applicability of our qubit proposal in the context of DiVincenzo’s criteria for the realization of local quantum computing processes. Altogether, the developed set of quantum operations would pave the way to the realization of a variety of quantum algorithms in a planar microcavity with a set of optically induced elliptical traps.

Dynamical evolution of exciton-polariton Bose-Einstein condensate under coupled interaction

Abstract We studied the exciton-polariton Bose-Einstein condensation (BEC) under light field manipulation by considering the coupled interaction of the system between exciton-polariton and light. Based on the coupled Gross-Pitaevskii equation (GPE) model and with modified variational method, we analytically derived the solutions of the excitonic system under the polar angle direction perturbation and system rotation. We identified that for different rotational angular velocities and different coupled strengths, the system evolves from a meta-stable oscillation state to monotonically decaying state, with potential for the study of quantum vortex identification for such kind of coupled systems. Our theoretical results can be used to guide the study of the evolution mode of the exciton-polariton system involving coupled interaction.

All-optical triangular and honeycomb lattices of exciton–polaritons

We implement an all-optically reconfigurable triangular lattice of exciton–polariton condensates in a III–V semiconductor microcavity. For this, we utilize a spatial light modulator to structure an incident nonresonant excitation laser beam into a corresponding triangular lattice of Gaussian beams that are focused onto the cavity plane. The optical excitation pattern locally stimulates and blueshifts polaritons due to exciton interactions. At a critical pump power, polaritons condense into a macroscopically coherent Bloch state with sharp Bragg peaks. We reconstruct the full band structure of the system through energy tomography techniques as a function of lattice constant, allowing us to resolve polaritonic Bloch bands from the condensate emission. While for sufficiently large lattice constants, one observes the formation of triangular arrays of condensates, for small lattice constant and pump powers above condensation threshold, one observes the formation of honeycomb, instead of triangular, lattice of condensates, with clear evidence of condensation into the S-band. Our results underpin the quality of all-optically engineered polariton lattices to simulate condensed matter systems in the strong coupling regime.

Compact gap solitons and compact edge states of exciton–polariton condensates with spin–orbit coupling in a one-dimensional flatband lattice

We propose that the compact gap solitons and compact edge states can be excited in a flatband of the incoherently-pumped exciton–polariton condensate under a one-dimensional periodic potential lattice. The combined effects of spin–orbit coupling and periodic potential depth on the flatband structures are investigated. Then how the compact gap solitons and edge states are localized and extended inside only a fraction of a single lattice site will be studied with varying pump strengths, pump spot-sizes as well as energy detuning.

Generation and modulation of shock waves in two-dimensional polariton condensates

Due to the ability of exciton-polariton condensates formed in semiconductor microcavities to be achieved at room temperature and their characteristics such as non-equilibrium and strong interactions,they have become an ideal platform for studying the nonlinear properties of non-equilibrium quantum systems.In 2013,the research group led by L.Dominici observed two-dimensional symmetric shock waves in the polariton condensate driven by coherent pump.However,owing to the characteristics of this system,theoretical researches have lagged behind.In one-dimensional polariton condensates,disregarding cross-interaction of the system,a type of asymmetric shock wave was respectively discovered by A.M.Kamchatnov in 2012 and A.M.Belounis in 2017.In 2023,utilizing the adiabatic approximation,our research team not only uncovered sparse wave,symmetric,and asymmetric shock waves in the system,but also revealed that the symmetric shock waves are triggered by cross-interaction.At present,there is no theoretical research on shock waves in two-dimensional polariton condensate.In this paper,spectral methods and fourth-order RungeKutta methods are used to explore the generation and control of shock waves in two-dimensional polariton condensates.It is found that when the cross-interaction between the condensate and the polariton thermal reservoir is quenched at high condensation rates,the initially prepared bright solitons can be modulated into two types of rotationally symmetric shock waves with different velocities,while the initial dark-like solitons can only transform into a single velocity rotationally symmetric shock wave.If quenching the external potential,the dark-like solitons can be transformed into anisotropic supersonic shock waves,and the dependence of shock wave on the width of the external potential is also shown.When the external potential and incoherent pumping are controlled at low condensation rates,multiple anisotropic shock waves can be excited in a uniform condensate,and their amplitudes can be used to control the wave number and amplitude of the shock waves and the range of widths for the external potential or incoherent pumping to excite shock waves is also demonstrated.The proposed methods in this paper not only provide theoretical guidance for the generation and control of shock waves in exciton-polariton condensates,but also find symmetric shock waves similar to experiments (Nat.Commun. <b>6</b> ,8993) without adopting any approximation,and open up a universal pathway for exciting shock waves in non-equilibrium or non-integrable systems,which may become a paradigm for transforming solitons into shock waves and significantly propel the rapid development of shock wave theory in different domains.

Optical trapping and tailoring of exciton-polariton condensates into macroscopic complexes

Optical trapping and tailoring of exciton-polariton condensates into macroscopic complexes

Polariton Condensation in Gap-Confined States of Photonic Crystal Waveguides.

The development of patterned multiquantum well heterostructures in GaAs/AlGaAs waveguides has recently made it possible to achieve exciton-polariton condensation in a topologically protected bound state in the continuum (BIC). Polariton condensation was shown to occur above a saddle point of the two-dimensional polariton dispersion in a one-dimensional photonic crystal waveguide. A rigorous analysis of the condensation phenomenon in these systems, as well as the role of the BIC, is still missing. In the present Letter, we theoretically and experimentally fill this gap by showing that polariton confinement resulting from the negative effective mass and the photonic energy gap in the dispersion play a key role in enhancing the relaxation toward the condensed state. In fact, our results show that low-threshold polariton condensation is achieved within the effective trap created by the exciting laser spot, regardless of whether the resulting confined mode is long-lived (polariton BIC) or short-lived (lossy mode). In both cases, the spatial quantization of the polariton condensate and the threshold differences associated to the corresponding state lifetime are measured and characterized. For a given negative mass, a slightly lower condensation threshold from the polariton BIC mode is found and associated to its reduced radiative losses, as compared to the lossy one.

Second-Order Temporal Coherence of Polariton Lasers Based on an Atomically Thin Crystal in a Microcavity.

Bosonic condensation and lasing of exciton polaritons in microcavities is a fascinating solid-state phenomenon. It provides a versatile platform to study out-of-equilibrium many-body physics and has recently appeared at the forefront of quantum technologies. Here, we study the photon statistics via the second-order temporal correlation function of polariton lasing emerging from an optical microcavity with an embedded atomically thin MoSe_{2} crystal. Furthermore, we investigate the macroscopic polariton phase transition for varying excitation powers and temperatures. The lower-polariton exhibits photon bunching below the threshold, implying a dominant thermal distribution of the emission, while above the threshold, the second-order correlation transits towards unity, which evidences the formation of a coherent state. Our findings are in agreement with a microscopic numerical model, which explicitly includes scattering with phonons on the quantum level.

Entanglement generation and detection in split exciton-polariton condensates

Entanglement generation and detection in split exciton-polariton condensates

Phase diagram of one-dimensional driven-dissipative exciton-polariton condensates

Phase diagram of one-dimensional driven-dissipative exciton-polariton condensates