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Résumé |
We discuss the capacitance and the resistance, usually called the charge
relaxation resistance, of a quantum coherent RC circuit driven by a
low-frequency AC voltage.
This circuit is the quantum analogue of the classical RC circuit:
it comprises a dot capacitively coupled to a nearby gate and connected
to a single reservoir lead. As a result of phase coherence and electronic
interactions, the quantum circuit behaves quite differently and
Kirchhoff's law is violated.
Here we show that the charge relaxation resistance is perfectly quantized,
regardless of the single lead transmission and for an arbitrary strength
of the interaction. Its low-frequency value is h/2 e^2.
When the driving frequency exceeds the dot level spacing, we predict
a transition to a metallic regime with a doubled quantized resistance h/e^2.
The novel quantized resistance h/e^2 is connected to the Korringa-Shiba
relation of the Kondo model, thereby revealing the physics behind these
universal charges.
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