Shot noise generated by graphene p-n junctions in the quantum Hall effect regime

TL;DR

This paper investigates shot noise in graphene p-n junctions under quantum Hall conditions, revealing how junction length influences mode mixing and energy relaxation, with implications for electron quantum optics.

Contribution

It demonstrates the role of p-n junction length in shot noise behavior and energy relaxation, advancing understanding of graphene's potential in quantum information applications.

Findings

Short PNJs exhibit behavior consistent with electronic beam-splitters.

Longer PNJs show reduced shot noise due to energy relaxation.

Relaxation length exceeds typical device sizes, enabling quantum optics applications.

Abstract

Owing to a linear and gapless band structure and a tunability of the charge carrier type, graphene offers a unique system to investigate transport of Dirac Fermions at p-n junctions (PNJs). In a magnetic field, combination of quantum Hall physics and the characteristic transport across PNJs leads to a fractionally quantized conductance associated with the mixing of electron-like and hole-like modes and their subsequent partitioning. The mixing and partitioning suggest that a PNJ could be used as an electronic beam-splitter. Here we report the shot noise study of the mode mixing process and demonstrate the crucial role of the PNJ length. For short PNJs, the amplitude of the noise is consistent with an electronic beam-splitter behavior, whereas, for longer PNJs, it is reduced by the energy relaxation. Remarkably, the relaxation length is much larger than typical size of mesoscopic devices, encouraging using graphene for electron quantum optics and quantum information processing.