Spin-polarized pumping in a double quantum dot

• Published in: Nanotechnology 2003-02, Vol.14 (2), p.152-156
• Main Authors: Cota, E, Aguado, R, Creffield, C E, Platero, G
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals; Exact sciences and technology; Physics; Single particle states
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/14/2/310

We study the pumping of spin-polarized electrons in a double quantum dot system with up to two electrons per dot, via an applied ac field and a constant magnetic field. The behavior of the current through the double-dot system is studied as a function of the ac field and coupling to the leads, using a Markov master equation approach for the time evolution of the reduced density matrix. For up to two electrons in the system, we find that the formation of a spin-triplet state blocks the current through the device, and analyze possible solutions. When we incorporate three-and four-particle states, with up to two opposite spin electrons per dot, we find a regime where the pumping of spin-polarized electrons is realized through double occupancy states in each dot. This property is robust against spin-relaxation and decoherence processes which are taken into account phenomenologically. Finally, we study the effects of applying a pulsed ac field and the possibility of the resolution of Rabi oscillations.