arXiv subjects

Stephan Roche

Publications and source records attributed to Stephan Roche.

132 records · Page 8Linked to original sources

arXiv2001

Backscattering in carbon nanotubes : role of quantum interference effects

For similar disorder, the backscattering contribution to the conductivity, irrelevant for metallic single-walled carbon nanotubes, is proved to become more significant for doped semiconducting systems, as found in experiments. In the case of multi-walled nanotubes, the intershell coupling is further shown to enhance the contribution of backscattering for "metallic" double-walled, whereas it remains insignificant for "metallic/semiconducting" double-walled systems. This supports that MWNTs are long ballistic conductors close to the charge neutrality point.

cond-mat.dis-nn↗

arXiv2001

Conduction mechanism and magnetotransport in multi-walled carbon nanotubes

We report on a numerical study of quantum diffusion over micron lengths in defect-free multi-walled nanotubes. The intershell coupling allows the electron spreading over several shells, and when their periodicities along the nanotube axis are incommensurate, which is likely in real materials, the electronic propagation is shown to be non ballistic. This results in magnetotransport properties which are exceptional for a disorder free system, and provides a new scenario to understand the experiments (A. Bachtold et al. Nature 397, 673 (1999)).

cond-mat.mtrl-sci↗

arXiv1999

Quantum interferences in quasicrystals

Contributions of quantum interference effects occuring in quasicrystals are emphasized. First conversely to metallic systems, quasiperiodic ones are shown to enclose original alterations of their conductive properties while downgrading long range order. Besides, origins of localization mechanisms are outlined within the context of the original metal-insulator transition (MIT) found in these materials.

cond-mat.mes-hall↗

arXiv1999

Anomalous electronic conductance in quasicrystals

Generic quantum interference effects occuring in 1D-quasicrystals are reviewed with emphasis on the joint effect of phason disorder on electronic localization and propagation modes. In close conjunction with properties of real materials, the contributions of quantum interferences in several regimes close to the metal insulator transition are outlined.

cond-mat.mtrl-sci↗

arXiv1999

A new formalism for the computation of RKKY interaction in aperiodic systems

A new formalism to investigate RKKY interaction in aperiodic materials is presented. Particularly useful in the tight-binding scheme, it is used in this paper to probe the role of local environment and long range quasiperiodic potential on this mesoscopic coupling. Interesting features are revealed and discussed within the context of anomalous localization and transport

cond-mat.mes-hall↗

arXiv1998

Effects of magnetic field and disorder on electronic properties of Carbon Nanotubes

Electronic properties of metallic and semiconducting carbon nanotubes are investigated in presence of magnetic field perpendicular to the CN-axis, and disorder introduced through energy site randomness. The magnetic field field is shown to induce a metal-insulator transition (MIT) in absence of disorder, and surprisingly disorder does not affect significantly the MIT. These results may find confirmation through tunneling experiments

cond-mat.mes-hall↗