Transport in serial spinful multiple-dot systems: The role of electron-electron interactions and coherences

TL;DR

This paper investigates how electron-electron interactions and quantum coherences influence electron transport in a spinful triple quantum dot system, revealing deviations from traditional layered quantum cascade laser models.

Contribution

It demonstrates the significant role of electron-electron scattering in enabling transport beyond single-particle channels and assesses the validity of different theoretical approaches for coherence effects.

Findings

Electron-electron interactions enable transport beyond single-particle channels.

Coherences are relevant when energy spacing is smaller than lead transition rate times ħ.

Transport deviates from layered quantum cascade laser behavior due to scattering processes.

Abstract

Quantum dots are nanoscopic systems, where carriers are confined in all three spatial directions. Such nanoscopic systems are suitable for fundamental studies of quantum mechanics and are candidates for applications such as quantum information processing. It was also proposed that linear arrangements of quantum dots could be used as quantum cascade laser. In this work we study the impact of electron-electron interactions on transport in a spinful serial triple quantum dot system weakly coupled to two leads. We find that due to electron-electron scattering processes the transport is enabled beyond the common single-particle transmission channels. This shows that the scenario in the serial quantum dots intrinsically deviates from layered structures such as quantum cascade lasers, where the presence of well-defined single-particle resonances between neighboring levels are crucial for device operation. Additionally, we check the validity of the Pauli master equation by comparing it with the first-order von Neumann approach. Here we demonstrate that coherences are of relevance if the energy spacing of the eigenstates is smaller than the lead transition rate multiplied by $\hbar$.