Cotunneling through two-level quantum dots weakly coupled to ferromagnetic leads

Abstract

The spin-polarized transport through two-level quantum dots weakly coupled to ferromagnetic leads is considered theoretically in the Coulomb blockade regime. It is assumed that the dot is doubly occupied, so that the current flows due to cotunneling through singlet and triplet states of the dot. It is shown that transport characteristics strongly depend on the ground state of quantum dot. If the ground state is a singlet, differential conductance ($G$) displays a broad minimum at low bias voltage, while tunnel magnetoresistance (TMR) is given by the Julliere value. If triplet is the ground state of the system, there is a maximum in differential conductance at zero bias when the leads are magnetized in antiparallel. The maximum is accompanied by a minimum in TMR. The different behavior of $G$ and TMR may thus help to determine the ground state of the dot and the energy difference between the singlet and triplet states.

to appear in EPL

References in corpus (6)

• Electric Field Control of Spin Transport
• Kondo effect in quantum dots coupled to ferromagnetic leads
• Tunnel magnetoresistance of quantum dots coupled to ferromagnetic leads in the sequential and cotunneling regimes
• Super-poissonian noise, negative differential conductance, and relaxation effects in transport through molecules, quantum dots and nanotubes
• Zero-bias anomaly in cotunneling transport through quantum-dot spin valves
• Gated Spin Transport through an Individual Single Wall Carbon Nanotube

Cited by in corpus (11)

• Spin effects in single electron tunneling
• Effects of different geometries on the conductance, shot noise and tunnel magnetoresistance of double quantum dots
• Transport through quantum-dot spin valves containing magnetic impurities
• Cotunneling through quantum dots coupled to magnetic leads: zero-bias anomaly for non-collinear magnetic configurations
• Influence of spin waves on transport through a quantum-dot spin valve
• Shot noise and tunnel magnetoresistance in multilevel quantum dots: Effects of cotunneling
• Spin-polarized transport through weakly coupled double quantum dots in the Coulomb-blockade regime
• Thermal broadening of the Coulomb blockade peaks in quantum Hall interferometers
• Theory of transport through noncollinear single-electron spin-valve transistors
• Co-tunneling current through the two-level quantum dot coupled to magnetic leads: A role of exchange interaction
• Current fluctuations of noncollinear single-electron spin-valve transistors