2 results
Search Results
Now showing 1 - 2 of 2
- ItemAttractive Dipolar Coupling between Stacked Exciton Fluids(College Park, Md. : APS, 2019) Hubert, Colin; Baruchi, Yifat; Mazuz-Harpaz, Yotam; Cohen, Kobi; Biermann, Klaus; Lemeshko, Mikhail; West, Ken; Pfeiffer, Loren; Rapaport, Ronen; Santos, PauloDipolar coupling plays a fundamental role in the interaction between electrically or magnetically polarized species such as magnetic atoms and dipolar molecules in a gas or dipolar excitons in the solid state. Unlike Coulomb or contactlike interactions found in many atomic, molecular, and condensed-matter systems, this interaction is long-ranged and highly anisotropic, as it changes from repulsive to attractive depending on the relative positions and orientation of the dipoles. Because of this unique property, many exotic, symmetry-breaking collective states have been recently predicted for cold dipolar gases, but only a few have been experimentally detected and only in dilute atomic dipolar Bose-Einstein condensates. Here, we report on the first observation of attractive dipolar coupling between excitonic dipoles using a new design of stacked semiconductor bilayers. We show that the presence of a dipolar exciton fluid in one bilayer modifies the spatial distribution and increases the binding energy of excitonic dipoles in a vertically remote layer. The binding energy changes are explained using a many-body polaron model describing the deformation of the exciton cloud due to its interaction with a remote dipolar exciton. The surprising nonmonotonic dependence on the cloud density indicates the important role of dipolar correlations, which is unique to dense, strongly interacting dipolar solid-state systems. Our concept provides a route for the realization of dipolar lattices with strong anisotropic interactions in semiconductor systems, which open the way for the observation of theoretically predicted new and exotic collective phases, as well as for engineering and sensing their collective excitations.
- ItemElectrically Driven Microcavity Exciton-Polariton Optomechanics at 20 GHz(College Park, Md. : APS, 2021) Kuznetsov, Alexander S.; Machado, Diego H.O.; Biermann, Klaus; Santos, Paulo V.Microcavity exciton polaritons enable the resonant coupling of excitons and photons to vibrations in the super-high-frequency (SHF, 3–30 GHz) domain. We introduce here a novel platform for coherent SHF optomechanics based on the coupling of polaritons and electrically driven SHF longitudinal acoustic phonons confined in a planar Bragg microcavity. The highly monochromatic phonons with tunable amplitudes are excited over a wide frequency range by piezoelectric transducers, which also act as efficient phonon detectors with a very large dynamical range. The microcavity platform exploits the long coherence time of polaritons as well as their efficient coupling to phonons. Furthermore, an intrinsic property of the platform is the backfeeding of phonons to the interaction region via reflections at the sample boundaries, which leads to quality factor × frequency products (Q×f) exceeding 1014 Hz as well as huge modulation amplitudes of the optical transition energies exceeding 8 meV. We show that the modulation is dominated by the phonon-induced energy shifts of the excitonic polariton component. Thus, the large modulation leads to a dynamical switching of light-matter nature of the particles from a mixed (i.e., polaritonic) one to photonlike and excitonlike states at frequencies up to 20 GHz. On the one hand, this work opens the way for electrically driven polariton optomechanics in the nonadiabatic, sideband-resolved regime of coherent control. Here, the bidirectionality of the transducers can be exploited for light-to-sound-to-rf conversion. On the other hand, the large phonon frequencies and Q×f products enable phonon control with optical readout down to the single-particle regime at relatively high temperatures (of 1 K).