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Summary: VOLUME 82, NUMBER 1 P H Y S I C A L R E V I E W L E T T E R S 4 JANUARY 1999
Observation of Quantum Fluctuations of Charge on a Quantum Dot
D. Berman,* N. B. Zhitenev,
and R. C. Ashoori
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
M. Shayegan
Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544
(Received 30 March 1998)
We have incorporated an aluminum single electron transistor directly into the defining gate structure
of a semiconductor quantum dot, permitting precise measurement of the dot charge. Voltage biasing
a gate draws charge from a reservoir into the dot through a single point contact. The dot charge
increases continuously for large point contact conductance and in single electron steps with the
contact nearly closed, and we measure the corresponding capacitance line shapes. The line shapes
are not typical of lifetime or thermal broadening but fit well to predictions of perturbation theory.
[S0031-9007(98)08102-2]
PACS numbers: 73.23.Hk, 72.15.Rn, 73.20.Fz
An isolated puddle of electrons (a quantum dot) holds a
discrete and measurable number of electrons. This remains
the case even if the puddle is weakly coupled to an electron
reservoir. The energetics of charging of quantum dots
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