Magnetoresistance and spin transport in organic semiconductors

Peter A. Bobbert 1Tho Nguyen 2Frank W. Van Oost 1Wiebe Wagemans 1Bert Koopmans 1Markus Wohlgenannt 2

1. Eindhoven University of Technology, Department of Physics, Eindhoven, Netherlands
2. Department of Physics and Astronomy, University of Iowa, Iowa City 52242-1479, United States

Abstract

The physics of spin dynamics and spin-spin interactions in organic semiconductors is completely different from their inorganic counterparts and this makes these semiconductors very interesting as new materials for spintronics. The most important differences are the following. 1) In contrast to inorganic semiconductors, the spin-orbit coupling in organic semiconductors appears to play an insignificant role, and it is in fact the hyperfine interaction with the hydrogen nuclear spins that dominates the dynamics of the electron spin. 2) Whereas inorganic semiconductors display band conduction, charge transport in organic semiconductors generally takes place by hopping conduction between localized states, due to disorder and small electron-transfer integrals. 3) While electron-phonon coupling in inorganic semiconductors is small and can be treated as a perturbation, such coupling is very important in organic semiconductors, leading to polaron formation and the possibility of bipolaron formation. New spin-related phenomena will be discussed in this presentation, such as the large intrinsic magnetoresistance of organic semiconductors and the peculiar behavior of the spin diffusion length as a function of temperature and external magnetic field. Novel theoretical frameworks will be presented in which these phenomena can be understood.

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Presentation: Invited oral at E-MRS Fall Meeting 2009, Symposium E, by Peter A. Bobbert
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-09 17:36
Revised:   2009-06-07 00:48
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