Transport of Neutral Optical Excitations Using Electric Fields

Cotleţ, Ovidiu; Pientka, Falko; Schmidt, Richard; Zaránd, Gergely; Demler, Eugene; İmamoğlu, Ataç

doi:10.1103/physrevx.9.041019

Cited by 34 publications

(32 citation statements)

References 67 publications

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“…which agrees with previous calculations using Green's functions [48]. This matrix element describes the amplitude for the emission of an electron-hole pair with momenta k and q by a polaron of momentum p. We emphasize that the above matrix element can also describe the residual interaction between the upper polaron-polariton and the Fermi sea, if we replace the coefficients ϕ and energy E p with the corresponding values for the upper polaron-polariton.…”

Section: Polaron-electron Interactionsupporting

confidence: 88%

Interacting Polaron-Polaritons

et al. 2020

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Two-dimensional semiconductors provide an ideal platform for exploration of linear exciton and polariton physics, primarily due to large exciton binding energy and strong light-matter coupling. These features, however, generically imply reduced exciton-exciton interactions, hindering the realization of active optical devices such as lasers or parametric oscillators. Here, we show that electrical injection of itinerant electrons into monolayer molybdenum diselenide allows us to overcome this limitation: dynamical screening of exciton-polaritons by electrons leads to the formation of new quasiparticles termed polaron-polaritons that exhibit unexpectedly strong interactions as well as optical amplification by Bose-enhanced polaron-electron scattering. To measure the nonlinear optical response, we carry out timeresolved pump-probe measurements and observe polaron-polariton interaction enhancement by a factor of 50 (0.5 μeV μm 2) as compared to exciton-polaritons. Concurrently, we measure a spectrally integrated transmission gain of the probe field of ≳2 stemming from stimulated scattering of polaron-polaritons. We show theoretically that the nonequilibrium nature of optically excited quasiparticles favors a previously unexplored interaction mechanism stemming from a phase-space filling in the screening cloud, which provides an accurate explanation of the strong repulsive interactions observed experimentally. Our findings show that itinerant electron-exciton interactions provide an invaluable tool for electronic manipulation of optical properties, demonstrate a new mechanism for dramatically enhancing polariton-polariton interactions, and pave the way for realization of nonequilibrium polariton condensates.

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Section: Polaron-electron Interactionsupporting

confidence: 88%

Interacting Polaron-Polaritons

et al. 2020

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“…The many-body polaronic states are expected to be charge neutral [31,32], suggesting the absence of coupling to external fields. In a recent theoretical study however, it was shown that neutral polarons are sensitive to the average force on electrons, leading to a finite polaron transconductivity in the non-equilibrium limit -an effect that is observable even when polarons hybridize with cavity photons [35].In the present work, we demonstrate experimentally that external electric and magnetic fields effect forces on polaron-polaritons. In contrast to earlier proposals, we find that the observed polariton acceleration primarily originates from a source-drain voltage induced density gradient in the two dimensional electron gas (2DEG) in which polaritons are immersed.…”

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“…By mapping the energy landscape of the lower polariton, we reach quantitative agreement between a simple trajectory based model and the observed polariton acceleration. Our experiment constitutes an alternative to the already proposed polariton drag effect for effecting electro-magnetic forces on neutral optical excitations [18,35]. We emphasize that the electron density gradients we exploit are generic for low density 2DEGs when large source-drain voltages are applied and therefore need to be considered in view of polariton drag experiments.…”

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Accelerating Polaritons with External Electric and Magnetic Fields

et al. 2020

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It is widely assumed that photons cannot be manipulated using electric or magnetic fields. Even though hybridization of photons with electronic polarization to form exciton-polaritons has paved the way to a number of ground-breaking experiments in semiconductor microcavities, the neutral bosonic nature of these quasiparticles has severely limited their response to external gauge fields. Here, we demonstrate polariton acceleration by external electric and magnetic fields in the presence of nonperturbative coupling between polaritons and itinerant electrons, leading to formation of new quasiparticles termed polaron-polaritons. We identify the generation of electron density gradients by the applied fields to be primarily responsible for inducing a gradient in polariton energy, which in turn leads to acceleration along a direction determined by the applied fields. Remarkably, we also observe that different polarization components of the polaritons can be accelerated in opposite directions when the electrons are in ν = 1 integer quantum Hall state.Controlling photons with external electric or magnetic fields is an outstanding goal. On the one hand, coupling photons to artificial gauge fields holds promises for the realization of topological and strongly correlated phases of light [1][2][3][4]. On the other hand, effecting forces on photons constitutes both a problem of fundamental interest in electromagnetism and an important step in view of technological applications [5][6][7][8]. One promising avenue towards this goal is to hybridize photons with material excitations that are genuinely sensitive to gauge fields [9]. In this non-perturbative regime, exciton-polariton states are formed, ensuring that the forces acting on the material excitations are directly imprinted onto the photon. However, the neutral bosonic nature of polaritons has so far severely limited their response to gauge fields [10][11][12][13].A particularly appealing approach to circumvent this limitation is to leverage on the interaction between excitons and charges. Indeed, early reports on the drift of trions in an electric field [14,15], as well as on the Coulomb drag effect in bilayer systems [16][17][18][19] indicated that it may be possible to manipulate neutral excitations using electric fields in a solid-state setting. Recently, experimental [20] and theoretical studies [21] reported the electrical control of the speed of a polariton superfluid, raising new questions and possibilities regarding the interplay between the normal and condensed fractions of the fluid in the presence of electron-exciton interactions.While interactions between polaritons and electrons have been proposed and analyzed as a mechanism for polariton thermalization [22][23][24][25], early studies reported the modifications to polariton resonances in the presence of a Fermi sea [26][27][28]. These modifications stem form dispersive interactions between the polarizable excitonic component of the polariton with the charge-density fluctuations of the Fermi sea [29][30][31]. ...

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“…More specifically, using time resolved four-wave mixing (FWM) experiments [28,29], we find that polariton-polariton interactions U can be enhanced by more than an order of magnitude around the fractional state at filling factor ν = 2/5 as compared to other neighboring compressible states. The interplay between photonic excitations and a 2DES is an exciting field [30][31][32][33][34] with open problems, among others, concerning the relation between transport and optics [35][36][37] and the description of exciton-electron interactions in a magnetic field [10].We study a semiconductor heterostructure that features, at the center of an optical microcavity, a GaAs QW containing an electron system of density n e = 3 × 10 10 cm −2 (see Methods). In the presence of a 2DES, electronexciton interactions modify the excitation spectrum and pioneering studies showed the existence of the strong coupling regime [38,39].…”

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Nonlinear optics in the fractional quantum Hall regime

Knüppel

Ravets

Kroner

et al. 2019

Nature

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These authors contributed equally to this work.Engineering strong interactions between optical photons is a great challenge for quantum science. Envisioned applications range from the realization of photonic gates for quantum information processing [1] to synthesis of photonic quantum materials for investigation of strongly-correlated drivendissipative systems [2]. Polaritonics, based on the strong coupling of photons to atomic or electronic excitations in an optical resonator, has emerged as a promising approach to implement those tasks [3]. Recent experiments demonstrated the onset of quantum correlations in the exciton-polariton system [4,5], showing that strong polariton blockade [6] could be achieved if interactions were an order of magnitude stronger. Here, we report time resolved four-wave mixing experiments on a two-dimensional electron system embedded in an optical cavity [7], demonstrating that polariton-polariton interactions are strongly enhanced when the electrons are initially in a fractional quantum Hall state. Our experiments indicate that in addition to strong correlations in the electronic ground state, exciton-electron interactions leading to the formation of polaron polaritons [8-11] play a key role in enhancing the nonlinear optical response. Besides potential applications in realization of strongly interacting photonic systems, our findings suggest that nonlinear optical measurements could provide information about fractional quantum Hall states that is not accessible in linear optical response.Polaritons have recently attracted considerable interest, motivated by the fact that their interactions can be engineered almost at will through the tunability of their matter component. For example, strongly interacting Rydberg polaritons have recently been obtained using the nonlinear behavior of Rydberg excitations in an ensemble of atoms [12], which led to the demonstration of Rydberg polariton blockade [13] where the presence of a single polariton in a well-delimited region of space prevents the resonant injection of other polaritons. In parallel, efforts are being made to realize polariton blockade in condensed matter systems that hold great potential for realizing compact and integrated synthetic quantum materials [3]. Exciton polaritons in semiconductor materials are part light part matter particles that arise from the strong coupling of a quantum well exciton and a cavity photon [14]. These photonic particles inherit a nonlinear behavior from exciton-exciton interactions [2,15,16]. For efficient blockade to be obtained, the nonlinearity U needs to be greater than the inverse lifetime γ of the polaritons [6]. Recent state-of-the art experiments based on photon correlation measurements in semi-integrated microcavities attained optimized values of the ratio U/γ 0.1 in a photonic dot with about 3 µm 2 area [4,5]. These experiments represent the culmination of decade long technological developments aimed at increasing U/γ through reducing the photonic mode area [17][18][19] as well as increasing t...

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Transport of Neutral Optical Excitations Using Electric Fields

Cited by 34 publications

References 67 publications

Interacting Polaron-Polaritons

Interacting Polaron-Polaritons

Accelerating Polaritons with External Electric and Magnetic Fields

Nonlinear optics in the fractional quantum Hall regime

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