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Strong localization in quasi one-dimensional systems with realistic defects: Application to carbon nanotubes

: Teichert, F.; Zienert, A.; Schuster, J.; Schreiber, M.

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European Electronic Structure Community:
Ψk Conference 2015. Abstract Book : September 6-10, 2015, Donostia, San Sebastian
San Sebastian, 2015
Psi-k Conference <2015, San Sebastian>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ENAS ()

Investigating the influence of disorder on electron transport is difficult for very large systems. These systems cannot be treated by conventional quantum transport theory (QTT) and accurate electronic structure theory like density functional theory (DFT) within appropriate time. But quasi one-dimensional systems (nanotubes, nanowires) with short-range interaction can in general be treated very efficiently using a linearly scaling recursive Green’s function formalism on the level of QTT. Additionally, describing the electronic structure by a density-functional-based tight-binding (DFTB) approach gives TB-simplicity and DFT-accuracy.We apply this formalism to carbon nanotubes (CNTs), which are a possible material for future microelectronic devices, overcoming the miniaturization problem. We calculate the conductance of metallic armchair CNTs with realistic defects, namely monovacancies and divacancies, within a statistical analysis. The exponential dependence on the number of defects shows that the system is in the strong localization regime (i.e. Anderson localization). Consequently, localization lengths can be extracted. We present the conductance and the localization length in dependence on defect density, temperature, and CNT diameter for different defect types. Furthermore, the influence of mixtures of defects is addressed. Finally, we show that the single-defect conductance is a good measure of disorder.