Counting statistics and super-Poissonian noise in a quantum dot

TL;DR

This paper reports time-resolved electron transport measurements through a quantum dot, revealing super-Poissonian noise and excited state dynamics using full counting statistics, with implications for understanding spin relaxation times.

Contribution

The study introduces a method to measure tunneling rates and detect super-Poissonian noise in a quantum dot using a quantum point contact as a charge detector.

Findings

Detection of electron bunching leading to super-Poissonian noise

Determination of individual tunneling rates through the barriers

Evidence of long relaxation times related to excited states

Abstract

We present time-resolved measurements of electron transport through a quantum dot. The measurements were performed using a nearby quantum point contact as a charge detector. The rates for tunneling through the two barriers connecting the dot to source and drain contacts could be determined individually. In the high bias regime, the method was used to probe excited states of the dot. Furthermore, we have detected bunching of electrons, leading to super-Poissonian noise. We have used the framework of the full counting statistics (FCS) to model the experimental data. The existence of super-Poissonian noise suggests a long relaxation time for the involved excited state, which could be related to the spin relaxation time.