Seiji Uryu

Carbon nanotube devices for nanoelectronics

We present a review of recent fundamental research on carbon nanotubes, with the goal of realizing future nanometer-scale electronic applications. Since nanotubes are by nature nanometer-scale devices with remarkable electrical properties, they are expected to be an important element in nanometer-scale electronics. As preliminary steps towards realizing nanotube-electronics, we have investigated the formation mechanism of metal contacts to carbon nanotubes, nanotube device fabrication possibilities, and nanotube spin electronics.

Electronic states and quantum transport in double-wall carbon nanotubes

The electronic states and transport properties of double-wall carbon nanotubes without impurities are studied in a systematic manner. It is revealed that scattering in the bulk is negligible and the number of channels determines the average conductance. In the case of general incommensurate tubes, separation of degenerated energy levels due to intertube transfer is suppressed in the energy region higher than the Fermi energy but not in the energy region lower than that. Accordingly, in the former case, there are few effects of intertube transfer on the conductance, while in the latter case, separation of degenerated energy levels leads to large reduction of the conductance. It is also found that in some cases antiresonance with edge states in inner tubes causes an anomalous conductance quantization

Electronic intertube transfer in double-wall carbon nanotubes with impurities : Tight-binding calculations

{G=e}^{2}/\ensuremath{\pi}\ensuremath{\Elzxh},

Quantum transport in antidot lattices

near the Fermi energy.

CHAOS AND QUANTUM TRANSPORT IN ANTIDOT LATTICES

Inter-tube conductance of double-wall carbon nanotubes with impurities is numerically studied. Its length dependence for various impurities is scaled by a mean-free path. The inter-tube conductance exhibits drastic linear increase with the tube length and takes a maximum around at the localization length. The maximum conductance is much smaller than the conductance quantum

Scattering-Matrix Formalism for Antidot Lattices

e^2/\pi\hbar

Magnetic field dependence of Coulomb oscillations in metal/multi-wall carbon nanotube/metal structures

.

Analysis of antidot lattices with periodic orbit theory

Abstract A review is given of quantum transport phenomena in antidot lattices mainly from a theoretical point of view. The topics include theoretical study performed for the purpose of understanding the origin of the commensurability peaks and its relation to the chaotic electron motion, the Aharonov-Bohm type oscillation and its relation to semiclassical quantization of periodic orbits, the Altshuler-Aronov-Spivak oscillation and roles of disorder in antidot potential itself, and an S matrix formalism in which antidot lattices are replaced by an array of quantum-wire junctions.

Breakdown of exchange approximation for cross-polarized excitons in carbon nanotubes

A review of magnetotransport in antidot lattices mainly from a theoretical point of view is given. The topics include various mechanisms proposed for the explanation of the origin of the commensurability peaks such as pinned orbits, runaway orbits, and diffusive orbits combined with a magnetic focusing effect. Roles of quantum effects and antidot disorder are also discussed.

Resistance dependence of transport properties in metal-multiwall carbon nanotube-metal structures

A method of full quantum mechanical calculation of energy bands of antidot lattices is developed based on a scattering (S) matrix which describes scattering at a junction of quantum wires. A comparison of calculated energy bands with results of diagonalization of the Hamiltonian in a lattice model shows that an S matrix including all traveling and a few evanescent modes gives a sufficiently accurate result.