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HL: Fachverband Halbleiterphysik
HL 48: Focus Session: Spintronics (jointly with MA)
HL 48.9: Talk
Wednesday, March 28, 2012, 12:15–12:30, EW 201
Dark-bright mixing of interband transitions in [111] grown semiconductor quantum dots — •Bernhard Urbaszek1, Gregory Sallen1, Misha Glazov2, Eougeniious Ivchenko2, Takashi Kuroda3, Takaaki Mano3, Sergej Kunz1, Kazuaki Sakoda3, Xavier Marie1, and Thierry Amand1 — 1Toulouse University, LPCNO-CNRS, France — 2Ioffe Institute, St.-Petersburg, Russia — 3NIMS, Tsukuba, Japan
Due to their inherently high symmetry, quantum dots grown along the [111] crystal axis have been indentified as suitable sources of entangled photon pairs via the exciton-biexction cascade [1]. We show that the underlying crystal symmetry does also result in highly unusual carrier spin physics probed in polarization resolved single dot photoluminescence spectroscopy. We observe for symmetric [111] grown GaAs/AlGaAs quantum dots in longitudinal magnetic fields applied along the growth axis in addition to the expected bright states also nominally dark transitions for both charged and neutral excitons. We uncover a strongly non-monotonous, sign changing field dependence of the bright neutral exciton splitting resulting from the interplay between exchange and Zeeman effects [2]. Our theory shows quantitatively that these surprising experimental results are due to magnetic-field-induced ± 3/2 heavy-hole mixing, an inherent property of systems with C3v point-group symmetry.
[1] Schliwa et al., PRB 80, 161307 (2009) & Singh and Bester, PRL 103, 063601 (2009) & Mohan et al., Nat. Photon. 4, 302 (2010)
[2] G. Sallen et al, Phys. Rev. Lett. 107, 166604 (2011)