2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

Low-T Quantum Transport in Carbon Nanotubes: Role of Vacuum Fluctuations in Loss of Phase Coherence

P.G. Gabrielli and S. Gabrielli
ENEA, IT

Keywords:
conductance, phase coherence, disorder

Abstract:
Among the items in the design of new generation of electronic devices there are the measurement and understanding of the current-voltage response of an electronic circuit in which molecular systems like carbon nanotubes (CNTs) act as conducting elements. Since the environment-induced decoherence is omnipresent in the microscopic world the destruction of phase coherence due to coupling of a system to an irreversible bath is a subject important because of its role in suppression of phenomena resulting from quantum interference effects such as Aharonov-Bohm interference, weak localization and universal conductance fluctuations. In a wire of length L and section A the conductance G=s(w,T)A/L is obtained by combination of smaller parts of materials if the temperature is so high that the conductivity s(w,T) can be treated as local quantity, but when the temperature is low (or the sample is small) the dephasing length Lf is greater than the sample linear dimensions so that the quantum corrections to the conductivity are non-local and the conductance can no longer be treated as a self-averaging quantity. The lack of self-averaging of the conductance is a feature of mesoscopic conductors so the study of quantum mechanical decoherence is a central problem in the physics of condensed matter systems coupled to an environment where, in the zero-temperature limit, the only source of decoherence are provided by vacuum fluctuations. Using a phenomenological approach we have analyzed the effects of random weak disorder induced by the vacuum fluctuations due to the presence of a conducting boundary on the electronics transport properties of CNTs, in particular the destruction of ballistic conduction in metallic carbon nanotubes due to loss of phase coherence.

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