Finite-frequency noise of interacting single-electron emitters: spectroscopy with higher noise harmonics

TL;DR

This paper analyzes the finite-frequency noise spectrum of a driven quantum dot acting as a single-electron emitter, revealing how Coulomb interactions and driving influence noise signatures and enabling spectroscopic insights into fluctuation processes.

Contribution

It extends a real-time diagrammatic technique to include finite-frequency noise and its harmonics in strongly interacting, driven quantum dots, providing new spectroscopic tools.

Findings

Identification of unique noise signatures due to Coulomb interaction and driving

Use of the first noise harmonic as a spectroscopic probe

Establishment of inverse noise frequency as a fluctuation time scale

Abstract

We derive the symmetrized current-noise spectrum of a quantum dot, which is weakly tunnel-coupled to an electron reservoir and driven by a slow time-dependent gate voltage. This setup can be operated as an on-demand emitter of single electrons into a mesoscopic conductor. By extending a real-time diagrammatic technique which is perturbative in the tunnel coupling, we obtain the time-resolved finite-frequency noise as well as its decomposition into noise harmonics in the presence of both strong Coulomb interaction and slow time-dependent driving. We investigate the noise over a large range of frequencies and point out where the interplay of Coulomb interaction and driving leads to unique signatures in finite-frequency noise spectra, in particular in the first harmonic. Besides that, we employ the first noise harmonic as a spectroscopic tool to access individual fluctuation processes. We discuss how the inverse noise frequency sets a time scale for fluctuations, which competes with time scales of the quantum-dot relaxation dynamics as well as the driving.