Negative tunnel magnetoresistance and differential conductance in transport through double quantum dots

TL;DR

This paper theoretically investigates spin-dependent transport in double quantum dots connected to ferromagnetic leads, revealing negative differential conductance and tunnel magnetoresistance effects influenced by coupling geometry and off-diagonal interactions.

Contribution

It introduces a comprehensive theoretical analysis of transport phenomena in double quantum dots, highlighting the impact of coupling geometry and virtual tunneling processes.

Findings

Negative differential conductance observed in serial and intermediate geometries.

Negative tunnel magnetoresistance found in certain configurations.

Transport properties strongly depend on off-diagonal coupling matrix elements.

Abstract

Spin-dependent transport through two coupled single-level quantum dots weakly connected to ferromagnetic leads with collinear magnetizations is considered theoretically. Transport characteristics, including the current, linear and nonlinear conductance, and tunnel magnetoresistance are calculated using the real-time diagrammatic technique in the parallel, serial, and intermediate geometries. The effects due to virtual tunneling processes between the two dots via the leads, associated with off-diagonal coupling matrix elements, are also considered. Negative differential conductance and negative tunnel magnetoresistance have been found in the case of serial and intermediate geometries, while no such behavior has been observed for double quantum dots coupled in parallel. It is also shown that transport characteristics strongly depend on the magnitude of the off-diagonal coupling matrix elements.