Berlin 2018 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 9: III-V semiconductors (other than nitrides)

HL 9.4: Vortrag

Montag, 12. März 2018, 15:45–16:00, EW 202

Mutual Indirect Exciton Interactions in Double Quantum Well Stacks — •Colin Hubert¹, Yifat Baruchi², Yotam Harpaz², Kobi Cohen², Ronen Rapaport², and Paulo Santos¹ — ¹Paul Drude Institut, Berlin, Deutschland — ²Racah Institut, Jerusalem, Israel

Indirect excitons (IXs) in double quantum well (DQW) structures subjected to a transverse electric field Ez form dipoles oriented along the field direction. The interaction between intraplanar IXs, i.e. IXs in the same DQW, is always repulsive. If, however, the IXs are placed in two different DQWs stacked along the z direction, the interaction becomes attractive as the dipoles orient themselves coaxially.

We have investigated the attraction between IXs in stacked DQW in GaAs structures by spatially resolved photoluminescence spectroscopy. The experiments are carried out by selectively exciting IXs in each of the two DQWs using tunable laser beams. Specifically the population in one of the wells is perturbed locally, while surrounded by a reservoir of IXs in the second well, whose population is kept constant. By observing the corresponding changes in density in the second DQW, we show the existence of the attractive interplanar interaction. The effect increases with increasing IX density. Single indirect exciton pairs in coupled DQWs stacks are predicted to have a very low binding energy of 0.2 meV. The IXs at high density show larger energy shifts and can reach as large as 4 meV. We will present both these results and our current understanding of interactions that cause a larger than predicted binding energy, especially at higher densities.