Full Counting Statistics for Number of Electrons Dwelling in a Quantum Dot

TL;DR

This paper analyzes the full counting statistics of electron numbers in a quantum dot, revealing non-Gaussian distributions and correlations with current, using advanced theoretical methods to derive cumulant generating functions.

Contribution

It introduces a comprehensive theoretical framework for calculating joint probability distributions of electron number and current in quantum dots, including new analytical results for various regimes.

Findings

Non-Gaussian exponential distribution when no dot state is near lead chemical potentials.

Measurement of joint probability distribution reveals correlations between current and electron number.

Quantum fluctuations significantly alter the electron number distribution with increasing tunneling strength.

Abstract

Motivated by recent real-time electron counting experiments, we evaluate the full counting statistics (FCS) for the probability distribution of the electron number inside a quantum dot which is weakly coupled to source and drain leads. A non-Gaussian exponential distribution appears when there is no dot state close to the lead chemical potentials. We propose the measurement of the joint probability distribution of current and electron number, which reveals correlations between the two observables. We also show that for increasing strength of tunneling, the quantum fluctuations qualitatively change the probability distribution of the electron number. In this paper, we derive the cumulant generating functions (CGFs) of the joint probability distribution for several cases. The Keldysh generating functional approach is adopted to obtain the CGFs for the resonant-level model and for the single-electron transistor in the intermediate conductance regime. The general form for the CGF of the joint probability distribution is provided within the Markov approximation in an extension of the master equation approach [D. A. Bagrets, and Yu. V. Nazarov, Phys. Rev. B {\bf 67}, 085316 (2003)].