Temporal Correlation of Electrons: Suppression of Shot Noise in a Ballistic Quantum Point Contact

Abstract

Wideband shot noise, associated with dc current flow through a quantum point contact (QPC), is measured in the microwave frequency range of 8-18 GHz. As the number of conducting channels in the QPC changes the noise power oscillates. Consistent with existing theories, the noise peaks depend linearly on the dc current. Surprisingly, however, in the pinch off region, where QPC is expected to behave as a classical injector, we find strong noise suppression, possibly mediated by the Coulomb interaction.

Supercurrent Noise in Quantum Point Contacts

“…There seems to be no reason to suspect that the situation should be any different in mesoscopic contacts with a few transverse modes, since, for instance, the noise properties of contacts in the normal state are insensitive to the number of transverse modes. Both in classical [2,3] and quantum [4,5] normal point contacts the shot noise was predicted to be suppressed due to the Pauli-principle correlations between electrons, and such a suppression has been found in experiments [6,7]. This picture is modified only slightly in point contacts between normal metals and superconductors, or in fully superconducting point contacts at large voltages, where Andreev scattering leads to partial reflection of electrons in the contact region giving rise to a finite level of shot noise [3,8].…”

Full shot noise in mesoscopic tunnel barriers

“…͑3͒ introduces shot noise suppression, which has been well studied in various systems. [2][3][4] On the other hand, if T n Ӷ 1 for all n, F Ϸ 1. While full shot noise was observed a long time ago in macroscopic systems, 5 such as semiconductor diodes, 6 it has been demonstrated only recently for mesoscopic tunnel barriers.…”

“…This has been verified experimentally. 2,3 As more negative voltages are applied, thus entering the pinch-off region where T n Ӷ 1, one would expect that full shot noise should be observed, according to Eq. ͑3͒.…”

Self-consistent theory of current and voltage noise in multimode ballistic conductors

“…This type of excess noise appears whenever there is a partitioning of current (T n 0;1). It vanishes for fully ballistic systems for which there is no partitioning (T n ϭ1) ͑see experimental evidence [7][8][9][10] ͒. In the absence of partitioning, the excess noise is in general no longer linear in the current.…”