Electron Waiting Time Distribution In Quantum Dot Transport System

Quantum transport involves the measurement of average current and shot noise in nanoscale conductors.In traditional studies,charge fluctuations are often studied over a long period of time,and the short-time behavior of electrons cannot be obtained from the average current.In order to describe the short-term physical properties in the mesoscopic structure and characterize the kinetic properties of a single electron,the concept of the waiting time distribution of the charge transfer is proposed.In this paper,based on tight-binding model and scattering theory,the waiting time distributions of electrons in single quantum dot system and T-type double quantum dot system are studied,respectively.The influence of system parameters on the distribution of waiting time is discussed.The following are the main contents and results of this article.(1)We study the electron waiting time distribution of single-level quantum dots coupled two leads.When the quantum dot energy level is aligned with the Fermi surface of the electrode,the waiting time distribution is independent of the bias voltage.When the quantum dot energy level deviates from the Fermi surface,as the bias voltage increases,the peak of distribution function increases and the waiting time distribution shifts towards shorter time.For a two-channel quantum dot system,the zero-time waiting time distribution is no longer zero and decreases as the quantum dot energy level deviates from the Fermi surface.With the temperature decreasing,the maximum value of waiting time distribution moves to a long time,and the maximum of distribution decreases slightly.However,the influence of temperature is mainly in the vicinity of the maximum distribution probability and has little effect on the long-term probability distribution.(2)We study the waiting time distribution of electrons in the T-type double quantum dot system.Since the electrons can reach the right electrode from the left electrode through two paths,when the interdot coupling is bigger than the coupling strength between the quantum dot and the wire and bias(or temperature)is lower,the waiting time distribution shows periodical minimum.With the decrease of the interdot coupling and the increase of the bias voltage(temperature difference),the periodical minimum gradually disappears.This is due to the fact that the interdot coupling between the two quantum dots of a T-type double quantum dot system provides two transport paths.