Optical emission from a charge-tunable quantum ring

Richard J Warburton

Department of Physics, Heriot-Watt University, Edinburgh EH14 4AS, UK

C. Schäflein, C. Schulhauser, D. Haft, F. Bickel, A. Lorke, and K. Karrai

Sektion Physik der LMU, Geschwister-Scholl-Platz 1, 80539 München, Germany

J. M. Garcia, W. Schoenfeld, and P. M. Petroff

Materials Department and QUEST, University of California Santa Barbara, California 93106, USA

Semiconductor quantum rings can be self-assembled using the growth of InAs on GaAs, largely as for quantum dots but with an additional annealing step. We have incorporated these quantum objects in a vertical transistor-like structure in order to study the effect of additional charge on the optical emission from excitons. In order to remove inhomogeneous broadening, we have performed these experiments on single quantum rings, monitoring the emission as electrons are added one by one¹. The experiments reveal the effects of Coulomb interactions between the confined electrons and holes, and we can determine the exciton’s polarisability and the spin-dependent relaxation rates. Furthermore, the results lead us to suggest the presence of temporal fluctuations in the local potential.

Very recent experiments have probed the consequences of the ring-like nature of the confining potential on the exciton, a neutral but compositie particle. To do this, we apply a magnetic field perpendicular to the rings. For some rings we observe a change in the diamagnetic shift of the neutral exciton’s emission at about 6 T. Simply from the geometry of the ring, this field corresponds closely to one flux quantum, suggesting that we have observed an Aharanov-Bohm type effect for an exciton.

^{1R. J. Warburton, C. Schäflein, D. Haft, F. Bickel, A. Lorke, K. Karrai, J. M. Garcia, W. Schoenfeld, and P. M. Petroff, Nature 405, 926 (2000).
^{2A. V. Chaplik, JETP Lett. 62, 900 (1995).
^{3R. A. Römer and M. E. Raikh, Phys. Rev. B 62, 7045 (2000).}}}