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HL: Fachverband Halbleiterphysik

HL 29: Quantum dots: Optical properties II

HL 29.11: Vortrag

Mittwoch, 25. März 2009, 12:30–12:45, BEY 154

All optical spin storage and readout in a single quantum dot — Dominik Heiss, Vase Jovanov, Florian Klotz, •Daniel Rudolph, Max Bichler, Martin S. Brandt, Gerhard Abstreiter, and Jonathan J. Finley — Walter Schottky Institut, Am Coulombwall 3, 85748 Garching, Germany

We propose an all optical spin readout method for single quantum dots (QDs) and demonstrate its feasibility. Our method involves using a voltage switchable QD spin memory structure that can be switched between two modes of operation: (i) charging, where optically generated holes are removed from the dot whilst electrons remain stored and (ii) readout, where optically generated carriers recombine to produce luminescence. The spin projection of a electron prepared using circularly polarized light during the charging phase of the measurement can be tested via a polarization conditional absorption of a second laser pulse tuned to the X- transition. This readout pulse converts the spin information of the resident electron into a charge occupancy (1e or 2e), which can then be repeatedly sampled during the readout phase of the measurement. The charging and discharging dynamics are probed using time dependent measurements to measure the tunneling escape time of the electron and hole. Furthermore, first measurements in magnetic fields (B=10 T) show indications of spin blockade during attempts to charge the dot with the second electron. This blockade can be lifted by delaying the 2e charging pulse by times longer than the electron spin relaxation time (T1~40 us).