Difference in charge and spin dynamics in a quantum dot-lead coupled system

TL;DR

This study investigates the distinct charge and spin relaxation dynamics in a quantum dot-lead system, revealing that spin relaxation is slower and depends on the quantum dot energy level, supported by experimental and theoretical analysis.

Contribution

It provides a detailed experimental and theoretical analysis of charge and spin dynamics in a quantum dot-lead system, highlighting the difference in relaxation times and their dependence on system parameters.

Findings

Spin relaxation is slower than charge relaxation.

Spin relaxation slows down as the quantum dot energy level decreases.

Theoretical model including first-order tunneling matches experimental results.

Abstract

We analyze time evolution of charge and spin states in a quantum dot coupled to an electric reservoir. Utilizing high-speed single-electron detection, we focus on dynamics induced by the first-order tunneling. We find that there is a difference between the spin and the charge relaxation: the former appears slower than the latter. The difference depends on the Fermi occupation factor and the spin relaxation becomes slower when the energy level of the quantum dot is lowered. We explain this behavior by a theory which includes the first-order tunneling processes. We conduct detailed comparison of the experiment and the theory with changing the energy of the quantum dot levels, and the theory can reproduce the experimental results.