Tunnelling magnetoresistance anomalies of a Coulomb blockaded quantum dot

TL;DR

This paper investigates tunnelling magnetoresistance anomalies in Coulomb blockaded quantum dots, revealing two distinct types caused by single-particle effects and electron correlations, with implications for experimental observations.

Contribution

It identifies and explains two types of TMR anomalies in quantum dots, linking them to single-particle effects and electron correlations, and discusses their behavior under various conditions.

Findings

TMR sign change at conductance resonances due to single-particle effects.

Enhanced TMR beyond 100% caused by electron correlations.

Anomalies are robust against temperature increases.

Abstract

We consider quantum transport and tunneling magnetoresistance (TMR) through an interacting quantum dot in the Coulomb blockade regime, attached to ferromagnetic leads. We show that there exist two kinds of anomalies of TMR, which have different origin. One type, associated with TMR sign change and appearing at conductance resonances, is of single particle origin. The second type, inducing a pronounced increase of TMR value far beyond 100%, is caused by electron correlations. It is manifested in-between Coulomb blockade conductance peaks. Both types of anomalies are discussed for zero and finite bias and their robustness to the temperature increase is also demonstrated. The results are presented in the context of recent experiments on semiconductor quantum dots in which similar features of TMR have been observed.