In this work we derive a theory of polariton condensation based on the theory of interacting Bose particles. In particular, we describe self-consistently the linear exciton-photon coupling and the exciton-nonlinearities, by generalizing the Hartree-Fock-Popov description of BEC to the case of two coupled Bose fields at thermal equilibrium. In this way, we compute the density-dependent one-particle spectrum, the energy occupations and the phase diagram. The results quantitatively agree with the existing experimental findings. We then present the equations for the linear response of a polariton condensate and we predict the spectral response of the system to external optical or mechanical perturbations.
By considering driven diffusive dynamics of exciton polaritons in an optical microcavity with an embedded molybdenum disulfide monolayer, we determine experimentally relevant range of parameters at which room-temperature superfuidity can be observed. It is shown that the superfluid transitions occurs in a trapped polariton gas at laser pumping power $P>600$ mW and and trapping potential strength $k > 50$ eV/cm$^2$. We also propose a simple analytic model that provides a useful estimate for the polariton gas density, which enables one to determine the conditions for observation of room temperat…
The spin Hall effect for polaritons (SHEP) in a transition metal dichalcogenides (TMDC) monolayer embedded in a microcavity is predicted. We demonstrate that two counterpropagating laser beams incident on a TMDC monolayer can deflect a superfluid polariton flow due to the generation the effective gauge vector and scalar potentials. The components of polariton conductivity tensor for both non-interacting polaritons without Bose-Einstein condensation (BEC)and for weakly-interacting Bose gas of polaritons in the presence of BEC and superfluidity are obtained. It is shown that the polariton flows …
We have developed a model of the nonlinear polariton dynamics in realistic 3D non-planar microcavity wires in the driven-dissipative regime. We find that the typical microcavity optical bistability evolves into multistability upon variation of the model parameters. The origin of the multistability is discussed in detail. We apply linear perturbation analysis to modulational instabilities, and identify conditions for localisation of composite multi-mode polariton solitons in the triggered parametric oscillator regime. Further, we demonstrate stable polariton soliton propagation in tilted and ta…
We present a precise calculation of spatially-indirect exciton states in semiconductor coupled quantum wells and polaritons formed from their coupling to the optical mode of a microcavity. We include the presence of electric and magnetic fields applied perpendicular to the quantum well plane. Our model predicts the existence of polaritons which are in the strong coupling regime and at the same time possess a large static dipole moment. We demonstrate, in particular, that a magnetic field can compensate for the reduction in light-matter coupling that occurs when an electric field impresses a di…
We explore the generation of anti-Stokes fluorescence from strongly coupled organic dye microcavities following resonant ground-state excitation. We observe polariton emission along the lower polariton branch, with our results indicating that this process involves a return to the exciton reservoir and the absorption of thermal energy from molecules in a vibrationally excited ground-state. We speculate that the generation of a population of "hot" polaritons is enhanced by the fact that the cavity supresses the emission of Stokes-shifted fluorescence, as it is located energetically below the cut…
We are interested in the emission characteristics of an atom interacting with the polaritonic excitations of a semiconductor or insulator embedded in a one-mode cavity. Since polaritons inside of the cavity exhibit intrinsic squeezing, we discuss how the squeezed polariton ground state modifies the atomic emission and how an indirect evidence of polariton squeezing outside of he cavity may be obtained.
We present a microcavity structure with a shifted photonic stop-band to enable efficient non-resonant injection of a polariton condensate with spectrally broad femtosecond pulses. The concept is demonstrated theoretically and confirmed experimentally for a planar GaAs/AlGaAs multilayer heterostructure pumped with ultrashort near-infrared pulses while photoluminescence is collected to monitor the optically injected polariton density. As the excitation wavelength is scanned, a regime of polariton condensation can be reached in our structure at a consistently lower fluence threshold than in a sta…
We describe exciton-polariton modes formed by the interaction between excitons in a 2D layer of a transition metal dichalcogenide embedded in a cylindrical microcavity and the microcavity photons. For this, an expression for the excitonic susceptibility of a semiconductor disk placed in the symmetry plane perpendicular to the axis of the microcavity is derived. Semiclassical theory provides dispersion relations for the polariton modes, while the quantum-mechanical treatment of a simplified model yields the Hopfield coefficients, measuring the degree of exciton-photon mixing in the coupled mode…
Nonlinear spectroscopy of exciton-polaritons in a GaAs-based microcavity
本文系统地研究了强耦合条件下GaAs基微腔中的双光子激发过程。我们观察到二次谐波产生共振的上，下极化激元的水平，这表现出很强的依赖于相应的极化激元的光子分数。此外，我们已经进行了双光子激发光谱，以确定$2p$激子状态，这是至关重要的操作作为太赫兹激光器件，这是最近提出的[A. V. Kavokin等人，物理修订信函\textbf{108}，197401（2012）]。然而，不能识别出$2p$激子态的明显特征，这表明双光子泵浦效率低。
We study tunable polaritons in monolayers of silicene, germanene, and stanene (Xenes) via an external electric field in an open optical microcavity whose length can be adjusted. An external electric field applied perpendicular to the plane of the Xene monolayer simultaneously changes the band gap and the exciton binding energy, while the variable length of the open microcavity allows one to keep the exciton and cavity photon modes in resonance. First, the Schrödinger equation for an electron and hole in an Xene monolayer is solved, yielding the eigenergies and eigenfunctions of the exciton as …
Microcavity polaritons are light-matter quasiparticles that arise from the strong coupling between excitons and photons confined in a semiconductor microcavity. They typically operate at visible or near visible wavelengths. They combine the properties of confined electromagnetic fields, including a sizeable spin-orbit coupling, and the sensitivity to external magnetic fields and particle interactions inherited from their partly matter nature. These features make polaritons an excellent platform to study topological phases in photonics in one and two dimensional lattices, which band properties …
Monolayer transition metal dichalcogenides, known for exhibiting strong excitonic resonances, constitute a very interesting and versatile platform for investigation of light-matter interactions. In this work we report on a strong coupling regime between excitons in monolayer WSe2 and photons confined in an open, voltage-tunable dielectric microcavity. The tunability of our system allows us to extend the exciton-polariton state over a wide energy range and, in particular, to bring the excitonic component of the lower polariton mode into resonance with other excitonic transitions in monolayer WS…
We investigate the statistics of microcavity polariton Bose-Einstein condensation by measuring photoluminescence dynamics from a GaAs microcavity excited by single laser excitation pulses. We directly observe fluctuations (jitter) of the polariton condensation onset time and model them using a master equation for the occupancy probabilities. The jitter of the condensation onset time is an inherent property of the condensate formation and its magnitude is approximately equal to the rise time of the condensate density. We investigate temporal correlations between the emission of condensate in op…
The formation and propagation of a polariton condensate under tightly focused excitation is investigated in a ZnO microcavity both experimentally and theoretically. 2D near-field and far-field images of the condensate are measured under quasi-continuous non-resonant excitation. The corresponding spatial profiles are compared to a model based on the Gross-Pitaevskii equation under cylindrical geometry. This work allows to connect the experiments performed with a small excitation laser spot and the previous kinetic models of condensation in a 2D infinite microcavity, and to determine the relevan…
The ultrafast scattering dynamics of intersubband polaritons in dispersive cavities embedding GaAs/AlGaAs quantum wells are studied directly within their band structure using a non-collinear pump-probe geometry with phase-stable mid-infrared pulses. Selective excitation of the lower polariton at a frequency of ~25 THz and at a finite in-plane momentum, $k_{||}$, leads to the emergence of a narrowband maximum in the probe reflectivity at $k_{||}=0$. A quantum mechanical model identifies the underlying microscopic process as stimulated coherent polariton-polariton scattering. These results mark …
We present a theoretical model that allows us to describe the dynamics of exciton polaritons in the strong-coupling regime in a monolayer WS2 based semiconductor microcavity. Numerical simulations using Boltzmann equations give an overall description of polariton kinetics over a temperature range of 130-230K, under nonresonant excitation. Here, only the scattering rate via optical phonons (LO) from the upper (UP) towards lower (LP) polariton branches is considered. According this model we show the importance of the radiative lifetime of the polaritonic states relative to polariton relaxation r…
Exciton-polaritons have become an emerging platform for implementing non-Hermitian physics. The implementation commonly requires control of both the real and imaginary parts of the eigenmodes of the system. We present an experimental method to achieve this purpose using microcavities with sub-wavelength gratings as reflectors. The reflectivity and reflection phase of the grating can be changed by its geometric parameters and they determine the energy and linewidth of the polariton modes. We demonstrate that this method allows a wide range of possible polariton energy and linewidth, suitable fo…
Electrical control over the energy exchange between exciton states mediated by cavity-polaritons at room temperature is demonstrated. Spatially separated field effect transistors based on monolayers of WS$_2$ and MoS$_2$ are placed in a tuneable Fabry-Pérot microcavity. This device is specially designed for the formation of exciton-polaritons that combine the two exciton species and a tuneable cavity mode. It is further shown that the tuning of the free carrier density in the WS$_2$ film leads to a strong modulation of the Rabi splitting that modifies the excitonic and photonic nature of excit…
