(Color online) (a) Room temperature scanning force microscope image of the quantum dot and the QPC formed by the bright oxide lines. The drain gate is labeled dg. (b) Charge stability diagram where the dot conductance is shown as a function of source-drain bias and tip voltage. Here the tip was at a constant position over the center of the dot. (c) The quantum dot conductance , (d) QPC current , and (e) QPC transconductance as functions of the tip voltage for the tip positioned over the center of the dot.
(Color online) (a)–(c) Scanning gate measurements of the coupled quantum dot and QPC system that were recorded simultaneously. (a) Conductance of the quantum dot. The black lines indicate the approximate position of the oxide lines that define the structure. The dashed line shows where the measurements of Figs. 3–5 were recorded. (b) Conductance of the QPC. (c) Transconductance of the QPC. (d) Overlay of rings from (a) (dashed green lines) and arcs from (c) (solid blue for dips and dotted red for peaks). Similar data have been presented in Ref. 20.
(Color online) (a) The dot conductance as a function of source-drain bias and the position of the tip measured along the dashed line in Fig. 2(a). By mapping the edges of the Coulomb diamonds it is possible to deduce (b) the tip-induced potential energy .
(Color online) (a) Dot conductance as a function of the voltage applied to the tip and the position of the tip, measured along the dashed line in Fig. 2(a). (b) The transconductance of the QPC measured simultaneously with the dot conductance. The arrow marks an anticrossing due to capacitive coupling between the dot and a charge trap.
(Color online) (a) The dot conductance and (b) the QPC transconductance as a function of the vertical distance between tip and sample and the position of the tip, measured along the dashed line in Fig. 2(a). (c) Three-dimensional representation of the QPC transconductance.
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