Invited Paper MI-WeA11
Spin Transport between Spin-Polarized Sources and Drains: Advantage of Carbon Nanotubes on Semiconductors

Wednesday, October 22, 2008, 5:00 pm, Room 206

Spin transport in a nonmagnetic lateral channel between a spin-polarized source and a spin-polarized drain is at the basis of several concepts of spin transistor. So far, the problem has been mainly studied for structures in which the nonmagnetic channel is a conventional semiconductor.¹ Spin injection into a semiconductor from a spin-polarized electrode begins to be well mastered. More difficult is the transformation of the spin information – related to the magnetic configuration of the electrodes- into a large electrical signal, ideally DV/V » 1 or larger, if V is the bias voltage and DV its variation when the magnetic configuration is changed. In experiments on structures in which the lateral channel is a semiconductor, DV/V does not generally exceed a few 1% and the electrical signal DV is only in the mV range.¹ In contrast, in the experiments on carbon nanotubes between ferromagnetic contacts we will present, high values of DV/V ( above 70%) and large DV (of the order of 100 mV) can be obtained.² After a description of the theoretical background, we will discuss the origin of the difficulties for semiconductors and explain why large values of DV/V and DV can be easily obtained with carbon nanotubes. We will emphasize the potential of carbon nanotubes, graphene and other molecules for spintronics, and conclude by presenting some next challenges for molecular spintronics.

¹ Jonker, B.T. and Flatté, M.E.F. Electrical spin injection and transport in semiconductors, in Nanomagnetism (eds. Mills D.L. & Bland J.A.C.) (Elsevier, 2006).
² Hueso, L. E., Pruneda J-M., Ferrari V., Burnell G., Valdés-Herrera J.P., Simons B.D., Littlewood P.B., Artacho E., Fert A. and Mathur N.D.. Transformation of spin information into large electrical signals via carbon nanotubes, Nature 445, 410 (2007).