Multi-quantum dot circuits with ferromagnetic contacts: from non-local spin effects to spin quantum bit setups
Résumé
Spin-dependent scattering of electrons at the interface between a ferromagnet and another material plays a central role in magnetic spin valves and multilayers celebrated by the Nobel prize of A. Fert and P. Grünberg in 2007. However, these devices do not exploit a crucial degree of freedom allowed by quantum mechanics: the orbital phase of the electronic wave function. In standard spin valves, a classical description is sufficient to describe the magnetoresistance effect. In the first part of this talk, I will discuss recent experiments of non-local spin-dependent transport in carbon nanotubes with ferromagnetic contacts [1]. These devices allow to study the interplay between electronic orbital coherence and spin-dependent scattering [2]. Our results bridge between mesoscopic physics and spin electronics, and pave the way for new spintronics devices which would exploit the coupling between the orbital phase and the spin degrees of freedom. In the second part of this talk, I will discuss how to use this "artificial spin-orbit coupling" to obtain an electric control of a single electronic spin. This effect can be obtained in a spin-quantum bit setup based on a double quantum dot with ferromagnetic contacts[3]. We also predict a switchable strong coupling to the photons confined in a superconducting coplanar waveguide cavity. This allows to envision on-chip single spin manipulation and read-out using cavity QED techniques. [1] C.Feuillet-Palma, T.Delattre, P.Morfin, J.-M.Berroir, G.Fève, D.C.Glattli, B.Plaçais, A.Cottet and T.Kontos, Phys. Rev. B 81, 115414 (2010). [2] A.Cottet, C.Feuillet-Palma, and T.Kontos, Phys. Rev. B 79, 125422 (2009). [3] A.Cottet and T.Kontos, arXiv:1005.1901