# Spin-polarized transport through weakly coupled double quantum dots in the Coulomb-blockade regime

## TL;DR

This paper investigates cotunneling transport in double quantum dots with ferromagnetic leads, revealing a zero-bias conductance peak, temperature-dependent tunnel magnetoresistance, and instances of negative TMR, highlighting complex spin-dependent quantum effects.

## Contribution

It provides a detailed analysis of cotunneling in double quantum dots, emphasizing the role of inter-dot Coulomb interaction and magnetic configurations in transport properties.

## Key findings

- Zero-bias conductance maximum conditioned by inter-dot Coulomb interaction
- TMR behavior varies with temperature, often independent of inter-dot correlation
- Negative TMR observed in certain bias voltage ranges

## Abstract

We analyze cotunneling transport through two quantum dots in series weakly coupled to external ferromagnetic leads. In the Coulomb blockade regime the electric current flows due to third-order tunneling, while the second-order single-barrier processes have indirect impact on the current by changing the occupation probabilities of the double dot system. We predict a zero-bias maximum in the differential conductance, whose magnitude is conditioned by the value of the inter-dot Coulomb interaction. This maximum is present in both magnetic configurations of the system and results from asymmetry in cotunneling through different virtual states. Furthermore, we show that tunnel magnetoresistance exhibits a distinctively different behavior depending on temperature, being rather independent of the value of inter-dot correlation. Moreover, we find negative TMR in some range of the bias voltage.