Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 19: Symposium Spin-Orbit Coupling and Spin Relaxation in Graphene and Carbon Nanotubes

O 19.6: Hauptvortrag

Montag, 22. März 2010, 17:10–17:45, H1

Spin transport in graphene field effect transistors — •Bart van Wees — Zernike Institute of Advanced Materials, University of Groningen, Groningen, The Netherlands

I will give an overview of electron spin injection, spin transport, spin precession and manipulation in graphene. The use of the so-called non-local geometry using graphene FET devices with ferromagnetic contacts allows a detailed experimental investigation. After a basic introduction I will discuss that: a) Spins can be transported through a graphene layer with a spin relaxation length of about 1.5 micrometer. By applying a perpendicular magnetic field Hanle spin precession can be studied and information about spin relaxation and the carrier diffusion can be obtained [1,3]. b) By applying a large DC electric field the transport of spins between injector and detector can be manipulated (sped up or slowed down) using carrier drift [2]. c) Spins can be injected with an injection efficiency up to 20 percent. This injection efficiency can be enhanced by a current bias which takes the carriers away from the injecting contacts [4]. d) We have observed a scaling between the spin relaxation times and lengths and the carrier mobility in graphene [5,6]. I will discuss the possibility that in clean intrinsic graphene spin relaxation lenghts of 100 micrometer in graphene at room temperature might be possible. [1] N. Tombros et al., Nature 448, 571 (2007)[2] N. Tombros et al., Phys. Rev. Lett. 101, 046601 (2008) [3] C. Jozsa et al., Phys. Rev. Lett. 100, 236603 (2008) [4] C. Jozsa et al., Phys. Rev. B 79, 081402 R (2009) [5] M. Popinciuc et al.,accepted for Phys. Rev. B. [6] C. Jozsa et al, Phys. Rev. B 80, 241403 (2009)