Full Counting Statistics in Multi-Terminal Normal Metal Tunnel Junction Structures

Abstract

Current fluctuations in multi-terminal structures are at the heart of mesoscopic physics (see Ref. [1]). The current noise power in small structures depends on correlations between charge transfer events. For example, in a one-channel conductor with transparency T the noise power at zero temperature is \( P_I = 2e\bar I(1 - T) \) [2, 3], where \( \bar I \) is the average current. The suppression factor 1 − T is a result of the Fermi correlation between electrons in different scattering events. An electron tunneling through the channel prevents the next electron from entering (‘antibunching’). Thus, the noise is suppressed in comparison to fully uncorrelated charge transfer (described by Schottky noise \( S_I = 2e\bar I \)). A convenient measure of the suppression is the Fano factor defined as \( F = P_I /2e\bar I. \) In the case of two tunnel junctions in series with conductances g 1(2), respectively, the Fano factor can be expressed as 2g 1 g 2/(g 1 + g 2)2. It is suppressed below 1 for all ratios of g 1 and g 2, again a consequence of the Pauli principle.