Mesoscopic charge quantization

Abstract

We study the Coulomb blockade in a chaotic quantum dot connected to a lead by a single channel at nearly perfect transmission. We take into account quantum fluctuations of the dot charge and a finite level spacing for electron states within the dot. Mesoscopic fluctuations of thermodynamic and transport properties in the Coulomb blockade regime exist at any transmission coefficient. In contrast to the previous theories, we show that by virtue of these mesoscopic fluctuations, the Coulomb blockade is not destroyed completely even at perfect transmission. The oscillatory dependence of all the observable characteristics on the gate voltage is preserved, its period is still defined by the charge of a single electron. However, phases of those oscillations are random; because of the randomness, the Coulomb blockade shows up not in the averages but in the correlation functions of the fluctuating observables (e.g., capacitance or tunneling conductance). This phenomenon may be called "mesoscopic charge quantization".