Sharp peaks in the conductance of double quantum dot and quantum dot spin-valve systems at high temperatures: A hierarchical quantum master equation approach

TL;DR

This paper investigates sharp conductance peaks near zero bias in double quantum dot and spin-valve systems at high temperatures, revealing a current suppression mechanism influenced by exchange interactions.

Contribution

It extends hierarchical quantum master equation methods to spin-valve systems, providing detailed analysis of conductance peaks and underlying physical mechanisms.

Findings

Sharp conductance peaks occur at high temperatures.

Exchange interactions cause bias-dependent current suppression.

Hierarchical quantum master equations reveal process contributions.

Abstract

We study sharp peaks in the conductance-voltage characteristics of a double quantum dot and a quantum dot spin-valve that are located around zero bias. The peaks share similarities with a Kondo peak but can be clearly distinguished, in particular as they occur at high temperatures. The underlying physical mechanism is a strong current suppression that is quenched in bias-voltage dependent ways by exchange interactions. Our theoretical results are based on the quantum master equation methodology, including the Born-Markov approximation and a numerically exact, hierarchical scheme, which we extend here to the spin-valve case. The comparison of exact and approximate results allows us to reveal the underlying physical mechanisms, the role of first-, second- and beyond-second-order processes and the robustness of the effect.