Enhanced and Suppressed Shot Noise in Quantum Dot Systems

Abstract

Quantum dots are quasi zero‐dimensional systems in semiconductors and they represent promising candidates for future applications in quantum information processing. Their electronic properties are influenced by interaction and correlation effects, which are not clearly revealed in simple transport experiments. Shot noise measurements allow to investigate such interaction and correlation effects in detail and can lead to astonishing results.We studied shot noise in electrical transport through single and coupled quantum dots and found for single quantum dots suppressed shot noise in respect to Poissonian noise as, e.g. is assumed in the recently developed technique of spin noise spectroscopy. Whereas the suppressed shot noise in single dots weakly coupled to the leads can be explained in simple models using emitter and collector tunnelling rates, for strong coupling an additional suppression is observed where interaction effects have to be taken into account. In recent measurements on coupled quantum dots an astonishing enhancement of shot noise, i.e. super‐Poissonian noise, was found being in stark contrast to the suppression of shot noise found for single quantum dots. This enhancement of shot noise cannot be understood in a single‐particle picture neglecting interactions. An enhanced shot noise could result from a coupling to other stacks of coupled quantum dots or from interaction and coherence effects within one stack.