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Sangalli D.,ETSF | Sangalli D.,University of Milan | Sangalli D.,University of Rome Tor Vergata | Marini A.,ETSF | And 2 more authors.
Nano Letters | Year: 2011

The gap oscillations caused by a magnetic flux penetrating a carbon nanotube represent one of the most spectacular observations of the Aharonov-Bohm effect at the nanoscale. Our understanding of this effect is, however, based on the assumption that the electrons are strictly confined on the tube surface, on trajectories that are not modified by curvature effects. Using an ab initio approach based on density functional theory, we show that this assumption fails at the nanoscale inducing important corrections to the physics of the Aharonov-Bohm effect. Curvature effects and electronic density that is spilled out of the nanotube surface are shown to break the periodicity of the gap oscillations. We predict the key phenomenological features of this anomalous Aharonov-Bohm effect in semiconductive and metallic tubes and the existence of a large metallic phase in the low flux regime of multiwalled nanotubes, also suggesting possible experiments to validate our results. © 2011 American Chemical Society. Source

Pulci O.,University of Rome Tor Vergata | Gori P.,ETSF | Gori P.,CNR Institute of Structure of Matter | Marsili M.,University of Rome Tor Vergata | And 7 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2010

The microscopic study of complex systems has reached a high level of accuracy that allows for a deep understanding of their structure, electronic properties, and optical spectra. The theoretical investigation of surfaces is nowadays routinely done within density functional theory, for ground state properties, and, with a larger computational load, within many-body perturbation theory, for excited states properties. In this paper we present and discuss examples of calculations for group IV two-dimensional systems such as a clean silicon surface, a tin-germanium interface, graphene, and graphane, pointing out the importance of a pertinent treatment of many-body effects. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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