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Anisotropic Dipolar Interactions in Indirect Exciton Bilayers

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If you have a question about this talk, please contact Dr Kaveh Delfanazari.

The dipolar interaction normally dominates the coupling between charge neutral species with a dipolar moment. Contrary to the isotropic Coulomb interaction, the dipolar coupling depends not only on the separation r between the dipoles but also on the angle θ between r and the dipole moment p. In particular, for collinear dipoles, the dipolar coupling turns from repulsive for large θ to attractive for cos 2 θ < 1/3. This anisotropic character gives rise to interesting phenomena in dipolar systems including pattern formation and instabilities in ferrofluids, liquid crystals, and Bose-Einstein condensates of dipolar species.[2] In this talk, we demonstrate that the attractive component of the dipolar interaction can bind aligned solid-state dipoles consisting of indirect excitons (IX) in two stacked double quantum well bilayers.[1] Each bilayer consists of two QWs separated by a thin tunneling barrier. A vertical electric field applied across the structure drives electrons and holes to different QWs, thus producing IX with a dipole moment aligned with the field. By using spatially and time-resolved photoluminescence spectroscopy, we show that the presence of a dipolar cloud in one bilayer changes the spatial distribution of IX dipoles in the other bilayer. The changes in spatial distribution are accompanied by an increase in the IX binding energy, which are accounted for by a polaron model for the IX-IX interaction. These results demonstrate the feasibility of dipolar control gates using stacked structures and open the way for the realization of interacting dipolar lattices in semiconductor systems. This project has received funding from the German DFG and the German-Israeli Foundation (GIF). * References [1] Colin Hubert, Yifat Baruchi, Yotam Mazuz-Harpaz, Kobi Cohen, Klaus Biermann, Mikhail Lemeshko, Ken West, Loren Pfeiffer, Ronen Rapaport, and Paulo Santos. Attractive dipolar coupling between stacked exciton fluids. Phys. Rev. X, 9:021026, May 2019. [2] T Lahaye, C Menotti, L Santos, M Lewenstein, and T Pfau. The physics of dipolar bosonic quantum gases. Rep. Prog. Phys., 72(12):126401, 2009.

This talk is part of the Semiconductor Physics Group Seminars series.

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