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

12 pages, 9 figgures

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• Effects of different geometries on the conductance, shot noise and tunnel magnetoresistance of double quantum dots
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• Electronic waiting-time distribution of a quantum-dot spin valve
• Transport through a double quantum dot system with non-collinearly polarized leads
• Probing the exchange field of a quantum-dot spin valve by a superconducting lead
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• Theory of shot noise in single-walled metallic carbon nanotubes weakly coupled to nonmagnetic and ferromagnetic leads
• Spin resonance without spin splitting
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• Duality for open fermion systems: energy-dependent weak coupling and quantum master equations
• Spin-resolved electron waiting times in a quantum dot spin valve
• Spin-polarized transport through weakly coupled double quantum dots in the Coulomb-blockade regime
• Role of coherence in transport through engineered atomic spin devices
• Proposal for a correlation induced spin-current polarizer
• Flavor fluctuations in 3-level quantum dots: Generic SU(3)-Kondo fixed point in equilibrium and non-Kondo fixed points in nonequilibrium
• The tunnel magnetoresistance in chains of quantum dots weakly coupled to external leads
• Spin transport properties of a quantum dot coupled to ferromagnetic leads with noncollinear magnetizations
• The generic fixed point model for pseudo-spin-1/2 quantum dots in nonequilibrium: Spin-valve systems with compensating spin polarizations