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TT: Fachverband Tiefe Temperaturen

TT 39: Transport: Nanoelectronics II - Spintronics and Magnetotransport

TT 39.4: Vortrag

Freitag, 29. Februar 2008, 11:15–11:30, EB 202

Spin transport across double quantum dots and carbon nanotubes — •S. Koller, R. P. Hornberger, G. Begemann, A. Donarini, and M. Grifoni — Institut für Theoretische Physik, Universität Regensburg, 93040 Regensburg

Spin polarized transport through nanostructures is a topic attracting increasing interest. Utilizing not only the charge, but also the electron’s spin degree of freedom opens various potential applications in spintronics as well as in quantum computing. Among the promising candidates for future electronic devices are e.g. carbon nanotubes as well as semiconducting quantum dots. By employing the reduced density matrix technique, we have developed a quite general model for spin dependent transport across nanostructures weakly coupled to ferromagnetic electrodes with both collinear or non-collinear magnetization directions. The model can be applied e.g. to single or double quantum dots [1] as well as to carbon nanotubes. For the two latter systems, the low bias conductance as a function of gate voltage exhibits a characteristic repeating pattern of four peaks distinct in height, possessing certain mirror symmetries representing electron-hole-symmetries. For devices like spin valve transistors, the tunnelling magnetoresistance (TMR) is a decisive parameter. It is found that the TMR is heavily influenced by a Zeeman splitting of energy levels, which in fact is not only crucial for the occurence of negative TMR, but also found to break the electron hole-symmetries. Overmore, in the nonlinear bias regime, negative differential conductance arises for non-collinear polarizations.
R. P. Hornberger et al., in preparation.