Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 88: Quantum Dots and Wires: Transport Properties IV (mainly Double Dots and Point Contacts)
HL 88.6: Vortrag
Donnerstag, 29. März 2012, 17:45–18:00, EW 202
Metastable charge states in a few electron double quantum dot — •Daniel Biesinger1, Martin Brühlmann1, Christian Scheller1, Dominik M. Zumbühl1, Jeramy Zimmerman2, and Art C. Gossard2 — 1Dep. of Physics, University of Basel, Switzerland — 2Materials Dep., University of California, Santa Barbara, California, USA
We are presenting quantum transport experiments on a lateral GaAs double quantum dot in the few electron regime. Adjacent quantum dots are used as real-time charge sensors, allowing single-shot charge readout with ms rise time and sensitivities as large as δ g / g ∼ 0.7 per electron. The tunneling-rates of the double dot can easily be widely tuned. At low enough dot-lead tunneling rates detectable in real-time, a sharply defined diamond-shaped region centered between the (0,0) and the (1,1) triple points appears in the charge stability diagram, displaying metastable charge-state switching between (0,1) and (1,0) as a function of time. The diamond is repeatable and does not show hysteresis. The timescale of the switching-process depends strongly on the coupling to source and drain, while it appears independent of the inter-dot coupling. The bistability disappears at higher tunneling-rates, returning to the usual honeycomb structure, but is also seen for larger electron numbers, making it unlikely that it is caused by random impurities or charge traps in a device that otherwise displays excellent stability. Further, we can rule out co-tunneling, latching and charge-sensor back action effects. We are currently looking for a model, and are in particular considering Fermi edge singularity physics.