event
Friday 26 Oct 2012: Colloquium: Graphene: The best material for spintronics?
Prof. Bart Van Wees - University of Groningen, The Netherlands
Newman F 12:00-13:00
I will first give an introduction into spintronics and show how the spin degree of freedom of the electrons can be used in a similar way as the charge degree of freedom in conventional electronics. The concepts of spin injection, spin accumulation, spin transport, spin precession and spin manipulation will be explained. This will be illustrated by experiments on graphene spintronic devices in my group done since 2007 when the first observation of spin transport and spin manipulation in a graphene field effect transistor was reported [1]. Promising aspects of graphene are that the spin-orbit interaction (the most important mechanism which can give rise to spin relaxation) is predicted to be very weak in graphene. In principle this would allow spins to be transported over macroscopic length scales (100 micrometer of more) without loss of their spin direction.
In will discuss the mechanisms which produce spin relaxation in practical devices, in particular the types of spin-orbit interaction, and how they depend on the graphene quality and graphene substrate [2,3,4,5] (exfoliated graphene on SiO2, graphene grown by chemical vapour deposition, graphene on silicon carbide and boron nitride, and freely suspended graphene). I will show that the ultimate potential of graphene for spintronics has not yet been established. In the meantime the experiments have shown that the electron spins in graphene are sensitive to their local environment, and can also be used to probe the (spin) states which are in proximity to the graphene, such as states in the substrate [5,6], or (magnetic) states in the specific molecules (e.g. hydrogen) which are deposited on top of the graphene [4] by either chemisorption or physisorption
References
[1] N. Tombros et al., Nature 448, 571 (2007)
[2] M. Guimaraes et al., Nano Letters 12(7), 3512 (2012)
[3] P. Zomer et al., arXiv: 1209.1999v1, submitted to Phys. Rev. Lett.
[4] M. Woijtaszek, in preparation
[5] T. Maassen et al., Nano Letters, 12 (3), 1498-1502 (2012)
[6] T. Maassen et al., arXiv:1208.3129v1, submitted to Phys. Rev. Lett.
