5,150 research outputs found
Electron transport through a quantum interferometer with side-coupled quantum dots: Green's function approach
We study electron transport through a quantum interferometer with
side-coupled quantum dots. The interferometer, threaded by a magnetic flux
, is attached symmetrically to two semi-infinite one-dimensional metallic
electrodes. The calculations are based on the tight-binding model and the
Green's function method, which numerically compute the conductance-energy and
current-voltage characteristics. Our results predict that under certain
conditions this particular geometry exhibits anti-resonant states. These states
are specific to the interferometric nature of the scattering and do not occur
in conventional one-dimensional scattering problems of potential barriers. Most
importantly we show that, such a simple geometric model can also be used as a
classical XOR gate, where the two gate voltages, viz, and , are
applied, respectively, in the two dots those are treated as the two inputs of
the XOR gate. For (, the elementary flux-quantum),
a high output current (1) (in the logical sense) appears if one, and only one,
of the inputs to the gate is high (1), while if both inputs are low (0) or both
are high (1), a low output current (0) appears. It clearly demonstrates the XOR
gate behavior and this aspect may be utilized in designing the electronic logic
gate.Comment: 8 pages, 5 figure
NAND gate response in a mesoscopic ring: An exact study
NAND gate response in a mesoscopic ring threaded with a magnetic flux
is investigated by using Green's function formalism. The ring is attached
symmetrically to two semi-infinite one-dimensional metallic electrodes and two
gate voltages, namely, and , are applied in one arm of the ring
those are treated as the two inputs of the NAND gate. We use a simple
tight-binding model to describe the system and numerically compute the
conductance-energy and current-voltage characteristics as functions of the gate
voltages, ring-to-electrode coupling strength and magnetic flux. Our
theoretical study shows that, for (, the
elementary flux-quantum) a high output current (1) (in the logical sense)
appears if one or both the inputs to the gate are low (0), while if both the
inputs to the gate are high (1), a low output current (0) appears. It clearly
exhibits the NAND gate behavior and this feature may be utilized in designing
an electronic logic gate.Comment: 8 pages, 5 figure
Quantum transport through molecular wires
We explore electron transport properties in molecular wires made of
heterocyclic molecules (pyrrole, furan and thiophene) by using the Green's
function technique. Parametric calculations are given based on the
tight-binding model to describe the electron transport in these wires. It is
observed that the transport properties are significantly influenced by (a) the
heteroatoms in the heterocyclic molecules and (b) the molecule-to-electrodes
coupling strength. Conductance () shows sharp resonance peaks associated
with the molecular energy levels in the limit of weak molecular coupling, while
they get broadened in the strong molecular coupling limit. These resonances get
shifted with the change of the heteroatoms in these heterocyclic molecules. All
the essential features of the electron transfer through these molecular wires
become much more clearly visible from the study of our current-voltage
(-) characteristics, and they provide several key informations in the
study of molecular transport.Comment: 8 pages, 4 figure
Flexible, textronic temperature sensors, based on carbon nanostructures
The paper presents a comparative analysis of two types of flexible temperature sensors, made of carbon-based nanostructures composites. These sensors were fabricated by a low-cost screen-printing method, which qualifies them to large scale, portable consumer electronic products. Results of examined measurements show the possibility of application for thick film devices, especially dedicated to wearable electronics, also known as a textronics. Apart from general characterisation, the influence of technological processes on specific sensor parameters were examined, particulary the value of the temperature coefficient of resistance (TCR) and its stability during the device bending
Stability of nonlinear elliptic systems with distributed parameters and variable boundary data
AbstractIn this paper nonlinear partial differential equations of the elliptic type with the Dirichlet boundary data are investigated. Some sufficient conditions under which the solutions of considered equations depend continuously on parameters and boundary conditions are proved. The proofs of main results are based on variational methods. In the final part of the paper we give a short survey of the results and methods related to the question of stability of the boundary value problems
Multi-Pulse Laser Wakefield Acceleration: A New Route to Efficient, High-Repetition-Rate Plasma Accelerators and High Flux Radiation Sources
Laser-driven plasma accelerators can generate accelerating gradients three
orders of magnitude larger than radio-frequency accelerators and have achieved
beam energies above 1 GeV in centimetre long stages. However, the pulse
repetition rate and wall-plug efficiency of plasma accelerators is limited by
the driving laser to less than approximately 1 Hz and 0.1% respectively. Here
we investigate the prospects for exciting the plasma wave with trains of
low-energy laser pulses rather than a single high-energy pulse. Resonantly
exciting the wakefield in this way would enable the use of different
technologies, such as fibre or thin-disc lasers, which are able to operate at
multi-kilohertz pulse repetition rates and with wall-plug efficiencies two
orders of magnitude higher than current laser systems. We outline the
parameters of efficient, GeV-scale, 10-kHz plasma accelerators and show that
they could drive compact X-ray sources with average photon fluxes comparable to
those of third-generation light source but with significantly improved temporal
resolution. Likewise FEL operation could be driven with comparable peak power
but with significantly larger repetition rates than extant FELs
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