Formulation of Kirchhoff Rod Based on Quasi-coordinates

The quasi-coordinates are applied to formulate Kirchhoff\u27s rod. The potential energy of the rod expressed by the quasi-coordinates has a similar form as the kinetic energy and complementary kinetic energy in dynamics. The conjugate quasi-momentum is defined and the canonical equations due to the quasi-coordinates are given. Kirchhoff\u27s equations can be derived directly from Boltzman-Hamel\u27s equations or its canonical form with arc length s as independent variables. Lagrange\u27s theorem is extended to determine the stability of equilibrium con-figuration of the elastic rod, and is proved using the Lyapunov\u27s direct method. It is noticed that the condition of stability has a different physical explanation than in dynamics

First-principles and model simulation of all-optical spin reversal

All-optical spin switching is a potential trailblazer for information storage and communication at an unprecedented fast rate and free of magnetic fields. However, the current wisdom is largely based on semiempirical models of effective magnetic fields and heat pulses, so it is difficult to provide high-speed design protocols for actual devices. Here, we carry out a massively parallel first-principles and model calculation for thirteen spin systems and magnetic layers, free of any effective field, to establish a simpler and alternative paradigm of laser-induced ultrafast spin reversal and to point out a path to a full-integrated photospintronic device. It is the interplay of the optical selection rule and sublattice spin orderings that underlines seemingly irreconcilable helicity-dependent/independent switchings. Using realistic experimental parameters, we predict that strong ferrimagnets, in particular, Laves phase C15 rare-earth alloys, meet the telecommunication energy requirement of 10 fJ, thus allowing a cost-effective subpicosecond laser to switch spin in the GHz region.Comment: 23 pages, 6 figures and one tabl

Scaling analysis of Schottky barriers at metal-embedded semiconducting carbon nanotube interfaces

We present an atomistic self-consistent tight-binding study of the electronic and transport properties of metal-semiconducting carbon nanotube interfaces as a function of the nanotube channel length when the end of the nanotube wire is buried inside the electrodes. We show that the lineup of the nanotube band structure relative to the metal Fermi-level depends strongly on the metal work function but weakly on the details of the interface. We analyze the length-dependent transport characteristics, which predicts a transition from tunneling to thermally-activated transport with increasing nanotube channel length.Comment: To appear in Phys.Rev.B Rapid Communications. Color figures available in PRB online versio