Different fractional charges from auto- and cross-correlation noise in quantum Hall states without upstream modes

TL;DR

This paper investigates how auto- and cross-correlation noise measurements in quantum Hall states can yield different fractional charge values, especially highlighting a new mechanism for excess auto-correlation noise in systems without upstream modes.

Contribution

It introduces a mechanism explaining excess auto-correlation noise in systems with multiple co-propagating edge modes, independent of upstream modes.

Findings

Auto-correlation noise can overestimate fractional charge due to multiple edge modes.

A new mechanism accounts for excess auto-correlation noise without upstream modes.

Differences in noise measurements affect fractional charge extraction in quantum Hall systems.

Abstract

Fractional charges of anyons can be extracted from shot noise in two ways. One can use either the auto-correlation noise of the current in one drain or the cross-correlation noise between two drains on the two sides of the device. The former approach typically overestimates the charge. This may happen due to upstream edge modes. We propose a mechanism for the excess auto-correlation noise without upstream modes. It applies to systems with multiple co-propagating edge modes and assumes that the noise is measured at a low but non-zero frequency.