Pauli spin blockade in weakly coupled quantum dots

TL;DR

This paper investigates Pauli spin blockade in a double quantum dot system, revealing how electron spin states and exchange interactions influence current suppression and flow in weakly coupled quantum dots.

Contribution

It demonstrates the role of interdot tunnelling, level offset, and exchange interactions in controlling spin blockade effects in coupled quantum dots.

Findings

Current is suppressed in one bias direction due to a triplet state.

Exchange interactions extend or reduce the blockade regime.

Occupation of two-electron states governs conductance behavior.

Abstract

In a two-level system, constituted by two serially coupled single level quantum dots, coupled to external leads we find that the current is suppressed in one direction of biasing caused by a fully occupied two-electron triplet state in the interacting region. The efficiency of the current suppression is governed by the ratio between the interdot tunnelling rate and the level off-set. In the opposite bias direction, the occupation of the two-electron triplet is lifted which allows a larger current to flow through the system, where the conductance is provided by transitions between one-electron states and two-electron singlet states. Is is also shown that a finite ferromagnetic interdot exchange interaction provides an extended range of the current suppression, while an anti-ferromagnetic exchange leads to a decreased range of the blockade regime.