17,078 research outputs found
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
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
Plasma-Like Negative Capacitance in Nano-Colloids
A negative capacitance has been observed in a nano-colloid between 0.1 and
10^-5 Hz. The response is linear over a broad range of conditions. The
low-omega dispersions of both the resistance and capacitance are consistent
with the free-carrier plasma model, while the transient behavior demonstrates
an unusual energy storage mechanism. A collective excitation, therefore, is
suggested.Comment: 3 pages, 3 figure
Scheme for remote implementation of partially unknown quantum operation of two qubits in cavity QED
By constructing the recovery operations of the protocol of remote
implementation of partially unknown quantum operation of two qubits [An Min
Wang: PRA, \textbf{74}, 032317(2006)], we present a scheme to implement it in
cavity QED. Long-lived Rydberg atoms are used as qubits, and the interaction
between the atoms and the field of cavity is a nonresonant one. Finally, we
analyze the experimental feasibility of this scheme.Comment: 7 pages, 2 figure
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