Attractive Dipolar Coupling between Stacked Exciton Fluids

Abstract

The interaction between aligned dipoles is long-ranged and highly anisotropic: it changes from repulsive to attractive depending on the relative positions of the dipoles. We report on the observation of the attractive component of the dipolar coupling between excitonic dipoles in 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 by a many-body polaron model describing the deformation of the exciton cloud due to its interaction with a remote dipolar exciton. The results open the way for the observation of theoretically predicted new and exotic collective phases, the realization of interacting dipolar lattices in semiconductor systems as well as for engineering and sensing their collective excitations. * These authors have equal contributions † hubert@pdi-berlin.de expansion and an interaction-driven phase transition between a gas and a state of self-bound, self-ordered liquid droplets, stabilized by the balance between attraction and repulsion and quantum fluctuations [2][3][4][5].

Attractive interactions, molecular complexes, and polarons in coupled dipolar exciton fluids

“…This binding energy for the sample used in Ref. 15 reaches only a few tens of meV and is thus much smaller than the measured interlayer binding energies. The calculations were carried out using the point charge approximation (PCA), which assumes that the electrons and holes constituting the IX to be described as point charges located at the center of the QWs.…”

“…6 of Ref. 15). It is interesting to note that depending on density, the inter-layer binding can thus be comparable to the intra-layer IX binding energy in GaAs QWs.…”

“…The large inter-layer binding energies reported in Ref. 15 were measured in an IX density regime, where the average separation between IXs within a DQW-bilayer is comparable to the separation between the bilayers, thus indicating that they may arise from many-body interaction effects, which are addressed in Sec. IV.…”

“…1(b)]. 15 These configuration enables the orientation of dipoles with angles θ < arccos [1/ √ 3]. The barrier between the two DQW bilayers was chosen to be sufficiently large to prevent single-particle tunneling but small enough to allow for electrostatic coupling between them.…”

Hybrid Semimagnetic Polaritons in a Strongly Coupled Optical Microcavity

“…Here, we demonstrate semimagnetic polaritons of a hybrid type, obtained thanks to the strong coupling of excitons confined in magnetic QWs (MQW) with excitons in nonmagnetic QWs (NMQW) and an optical mode of a microcavity. The hybridization takes place over a distance of the order of 100 nm, which exceeds the range of tens of nanometers relevant for a dipolar polariton 28 − 30 or exciton quantum tunnelling regime. 31 − 33 Thanks to the optical-mode mediated coupling, the susceptibility of the excitons in the MQW to the magnetic field is extended over all hybrid polariton states arising in the structure.…”