244 research outputs found
Metamaterials for Ballistic Electrons
The paper presents a metamaterial for ballistic electrons, which consists of
a quantum barrier formed in a semiconductor with negative effective electron
mass. This barrier is the analogue of a metamaterial for electromagnetic waves
in media with negative electrical permittivity and magnetic permeability.
Besides applications similar to those of optical metamaterials, a nanosized
slab of a metamaterial for ballistic electrons, sandwiched between quantum
wells of positive effective mass materials, reveals unexpected conduction
properties, e.g. single or multiple room temperature negative differential
conductance regions at very low voltages and with considerable peak-to-valley
ratios, while the traversal time of ballistic electrons can be tuned to larger
or smaller values than in the absence of the metamaterial slab. Thus, slow and
fast electrons, analogous to slow and fast light, occur in metamaterials for
ballistic electrons
Writing Electronic Devices on Paper with Carbon Nanotube Ink
The normal paper used in any printer is among the cheapest flexible organic
materials that exist. We demonstrate that we can print on paper high-frequency
circuits tunable with an applied dc voltage. This is possible with the help of
an ink containing functionalized carbon nanotubes and water. After the water is
evaporated from the paper, the nanotubes remain steadily imprinted on paper,
showing a semiconducting behaviour and tunable electrical properties
Phase Space Formulation of Quantum Mechanics. Insight into the Measurement Problem
A phase space mathematical formulation of quantum mechanical processes
accompanied by and ontological interpretation is presented in an axiomatic
form. The problem of quantum measurement, including that of quantum state
filtering, is treated in detail. Unlike standard quantum theory both quantum
and classical measuring device can be accommodated by the present approach to
solve the quantum measurement problemComment: 29 pages, 4 figure
Graphene-like metallic-on-silicon field effect transistor
In this manuscript, we present a field effect transistor with a channel
consisting of a two-dimensional electron gas located at the interface between
an ultrathin metallic film of Ni and a p-type Si(111) substrate. We have
demonstrated that the two-dimensional electron gas channel is modulated by the
gate voltage. The dependence of the drain current on the drain voltage has no
saturation region, similar to a field effect transistor based on graphene.
However, the transport in this transistor is not ambipolar, as in graphene, but
unipolar
Microwave Inter-Connections and Switching by means of Carbon Nano-tubes
In this work, carbon nanotube (CNT) based
interconnections and switches will be reviewed,
discussing the possibility to use nanotubes as potential
building blocks for signal routing in microwave
networks. In particular, theoretical design of coplanar
waveguide (CPW), microâstrip singleâpoleâsingleâthrow
(SPST) and singleâpoleâdoubleâthrow (SPDT) devices has
been performed to predict the electrical performances of
CNTâbased RF switching configurations. Actually, by
using the semiconductorâconductor transition obtained
by properly biasing the CNTs, an isolation better than 30
dB can be obtained between the ON and OFF states of the
switch for very wide bandwidth applications. This
happens owing to the shape deformation and consequent
change in the bandâgap due to the external pressure
caused by the electric field. Stateâofâart for other
switching techniques based on CNTs and their use for RF
nanoâinterconnections is also discussed, together with
current issues in measurement techniques
Experimental determination of microwave attenuation and electrical permittivity of double-walled carbon nanotubes
The attenuation and the electrical permittivity of the double-walled carbon nanotubes (DWCNTs) were determined in the frequency range of 1â65 GHz. A micromachined coplanar waveguide transmission line supported on a Si membrane with a thickness of 1.4 ”m was filled with a mixture of DWCNTs. The propagation constants were then determined from the S parameter measurements. The DWCNTs mixture behaves like a dielectric in the range of 1â65 GHz with moderate losses and an abrupt change of the effective permittivity that is very useful for gas sensor detection. ©2006 American Institute of Physic
Classical simulation of Quantum Entanglement using Optical Transverse Modes in Multimode Waveguides
We discuss mode-entangled states based on the optical transverse modes of the
optical field propagating in multi-mode waveguides, which are classical analogs
of the quantum entangled states. The analogs are discussed in detail, including
the violation of the Bell inequality and the correlation properties of optical
pulses' group delays. The research on these analogs may be important, for it
not only provides useful insights into fundamental features of quantum
entanglement, but also yields new insights into quantum computation and quantum
communication.Comment: RevTeX v4, 17 pages and 4 figure
Very large phase shift of microwave signals in a 6 nm Hf x Zr 1â x O 2 ferroelectric at ±3 V
In this letter, we report for the first time very large phase shifts of microwaves in the 1â10 GHz range, in a 1 mm long gold coplanar interdigitated structure deposited over a 6 nm Hf x Zr1âx O2 ferroelectric grown directly on a high resistivity silicon substrate. The phase shift is larger than 60° at 1 GHz and 13° at 10 GHz at maximum applied DC voltages of ±3 V, which can be supplied by a simple commercial battery. In this way, we demonstrate experimentally that the new ferroelectrics based on HfO2 could play an important role in the future development of wireless communication systems for very low power applications
Field-induced decay of quantum vacuum: visualizing pair production in a classical photonic system
The phenomenon of vacuum decay, i.e. electron-positron pair production due to
the instability of the quantum electrodynamics vacuum in an external field, is
a remarkable prediction of Dirac theory whose experimental observation is still
lacking. Here a classic wave optics analogue of vacuum decay, based on light
propagation in curved waveguide superlattices, is proposed. Our photonic
analogue enables a simple and experimentally-accessible visualization in space
of the process of pair production as break up of an initially negative-energy
Gaussian wave packet, representing an electron in the Dirac sea, under the
influence of an oscillating electric field
Coherent tunneling by adiabatic passage in an optical waveguide system
We report on the first experimental demonstration of light transfer in an
engineered triple-well optical waveguide structure which provides a classic
analogue of Coherent Tunnelling by Adiabatic Passage (CTAP) recently proposed
for coherent transport in space of neutral atoms or electrons among
tunneling-coupled optical traps or quantum wells [A.D. Greentree et al., Phys.
Rev. B 70, 235317 (2004); K. Eckert et al., Phys. Rev. A 70, 023606 (2004)].
The direct visualization of CTAP wavepacket dynamics enabled by our simple
optical system clearly shows that in the counterintuitive passage scheme light
waves tunnel between the two outer wells without appreciable excitation of the
middle well.Comment: submitted for publicatio
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