Mesoscopic versus Macroscopic Division of Current Fluctuations

We investigate the current shot noise at a three terminal node in which one of the branches contains a noise generating source and the correlations are measured between the currents flowing through the other two branches. Interestingly, if the node is macroscopic, the current correlations are positive, whereas for a quantum coherent mesoscopic node antibunching of electrons leads to negative correlations. We present specific predictions which permit the experimental investigation of the crossover from the quantum mechanical noise division to the macroscopic noise division.

Figure 1

Macroscopic and mesoscopic division of shot noise. The macroscopic classical circuit of Fig. 1a contains one source of noise $i_1(t)$. Fluctuations induced by this source give rise to a positive current correlation between currents at leads 2 and 3. Figure 1b represents a mesoscopic conductor which exhibits negative correlations. $G_i$ are contact conductances.

Figure 2

Ensemble averaged current-current correlation as a function of transmission probability $\Gamma$. The full and broken lines are the analytical results of the semiclassical theory. The open symbols are from a numerical integration over an ensemble of random matrices for different symmetry classes $\beta =1,2$ and different number of channels $N_p$ of the voltage probe.

Figure 3

Distribution of the shot noise correlation for a mesoscopic cavity. The cavity is connected via a noise generating contact with transmission $\Gamma$ per channel and two perfect contacts to reservoirs. For the case of two channels per contact and 15 channels in the voltage probe the transition from negative to positive correlations is near $\Gamma =0.5$.