Cotunneling through quantum dots coupled to magnetic leads: zero-bias anomaly for non-collinear magnetic configurations

TL;DR

This paper theoretically investigates cotunneling through quantum dots with non-collinear magnetic leads, revealing how exchange fields influence transport properties like conductance and tunnel magnetoresistance, especially near zero bias.

Contribution

It introduces a detailed analysis of how ferromagnetic lead-induced exchange fields affect quantum dot transport in non-collinear configurations, including spin precession effects.

Findings

Exchange field modifies zero-bias anomalies.

Non-monotonic conductance dependence on magnetic angle.

Enhanced conductance and negative TMR in certain configurations.

Abstract

Cotunneling transport through quantum dots weakly coupled to non-collinearly magnetized leads is analyzed theoretically by means of the real-time diagrammatic technique. The electric current, dot occupations, and dot spin are calculated in the Coulomb blockade regime and for arbitrary magnetic configuration of the system. It is shown that an effective exchange field exerted on the dot by ferromagnetic leads can significantly modify the transport characteristics in non-collinear magnetic configurations, in particular the zero-bias anomaly found recently for antiparallel configuration. For asymmetric Anderson model, the exchange field gives rise to precession of the dot spin, which leads to a nonmonotonic dependence of the differential conductance and tunnel magnetoresistance on the angle between magnetic moments of the leads. An enhanced differential conductance and negative TMR are found for certain non-collinear configurations.