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

Abstract

Dipolar (or spatially indirect) excitons (IXs) in semiconductor double quantum well (DQW) subjected to an electric field are neutral species with a dipole moment oriented perpendicular to the DQW plane. Here, we theoretically study interactions between IXs in stacked DQW bilayers, where the dipolar coupling can be either attractive or repulsive depending on the relative positions of the particles. By using microscopic band structure calculations to determine the electronic states forming the excitons, we show that the attractive dipolar interaction between stacked IXs deforms their electronic wave function, thereby increasing the inter-DQW interaction energy and making the IX electrically polarizable. Many-particle effects interaction are addressed by considering the coupling between a single IX in one of the DQWs to a cloud of IXs in the other DQW, which is modeled either as a closed-packed lattice or as a continuum IX fluid. We find that the lattice model yields IX interlayer binding energies decreasing with increasing lattice density. This behavior is due to the dominating role of the intra-DQW dipolar repulsion, which prevents more than one exciton from entering the attractive region of the inter-DQW coupling. Finally, both models shows that the single IX distorts the distribution of IXs in the adjacent DQW, thus inducing the formation of an IX polaron. While the interlayer binding energy reduces with IX density for lattice polarons, the continuous polaron model predicts a non-monotonous dependence on density in semi-quantitative agreement with a recent experimental study [cf. Hubert {\it et al.}, Phys. Rev. {\bf X}9, 021026 (2019)].

arXiv comment12 figures, 12 pages

References in corpus (20)

• The physics of dipolar bosonic quantum gases
• Bose-Einstein Condensation of Excitons in Bilayer Electron Systems
• Observing the Rosensweig instability of a quantum ferrofluid
• Roton-maxon spectrum and stability of trapped dipolar condensates
• Quantum-fluctuation-driven crossover from a dilute Bose-Einstein condensate to a macro-droplet in a dipolar quantum fluid
• Observation of a dipolar quantum gas with metastable supersolid properties
• Strong dipolar effects in a quantum ferrofluid
• Transient supersolid properties in an array of dipolar quantum droplets
• Spontaneous Coherence in a Cold Exciton Gas
• Observation of Roton Mode Population in a Dipolar Quantum Gas
• Exciton correlations in coupled quantum wells and their luminescence blue shift
• Exciton Liquid in Coupled Quantum Wells
• A dark incompressible dipolar liquid of excitons
• Effects of strong correlations for 2D Bose-Einstein condensed dipolar excitons
• Ground-state properties of Dipolar Bose polarons
• Phases of dipolar bosons in a bilayer geometry
• Structure and melting behavior of classical bilayer crystals of dipoles
• Attractive dipolar coupling between stacked exciton fluids
• An efficient finite-difference scheme for computation of electron states in free-standing and core-shell quantum wires
• Vertically-coupled dipolar exciton molecules

Cited by in corpus (2)

• Collective interlayer pairing and pair superfluidity in vertically stacked layers of dipolar excitons
• Attractive and repulsive dipolar interaction in bilayers of indirect excitons