38 research outputs found
Possible cooling by resonant Fowler-Nordheim emission
A new method of electronic refrigeration based on resonant Fowler-Nordheim
emission is proposed and analyzed. In this method, a bulk emitter is covered
with a-few-nm-thick film of a widegap semiconductor, creating an intermediate
step between electron energies in the emitter and in vacuum. An external
electric field tilts this potential profile, forming a quantum well, and hence
2D electron subbands at the semiconductor-vacuum boundary. Alignment of the
lowest subband with the energy levels of the hottest electrons of the emitter
(a few above its Fermi level) leads to a resonant, selective emission
of these electrons, providing emitter cooling. Calculations show that cooling
power as high as 10^{4} W/cm^{2} (at 300 K), and temperatures down to 10 K may
be achieved using this effect.Comment: 4 pages, 2 figure
Single-Electron Parametron: Reversible Computation in a Discrete State System
We have analyzed energy dissipation in a digital device (``Single-Electron
Parametron'') in which discrete degrees of freedom are used for presenting
digital information. If the switching speed is not too high, the device may
operate reversibly (adiabatically), and the energy dissipation per
bit may be much less than the thermal energy . The energy-time product
is, however, much larger than Planck's constant , at
least in the standard ``orthodox'' model of single-electron tunneling, which
was used in our calculations.Comment: 9 pages, RevTex, 3 figure
Capacity, Fidelity, and Noise Tolerance of Associative Spatial-Temporal Memories Based on Memristive Neuromorphic Network
We have calculated the key characteristics of associative
(content-addressable) spatial-temporal memories based on neuromorphic networks
with restricted connectivity - "CrossNets". Such networks may be naturally
implemented in nanoelectronic hardware using hybrid CMOS/memristor circuits,
which may feature extremely high energy efficiency, approaching that of
biological cortical circuits, at much higher operation speed. Our numerical
simulations, in some cases confirmed by analytical calculations, have shown
that the characteristics depend substantially on the method of information
recording into the memory. Of the four methods we have explored, two look
especially promising - one based on the quadratic programming, and the other
one being a specific discrete version of the gradient descent. The latter
method provides a slightly lower memory capacity (at the same fidelity) then
the former one, but it allows local recording, which may be more readily
implemented in nanoelectronic hardware. Most importantly, at the synchronous
retrieval, both methods provide a capacity higher than that of the well-known
Ternary Content-Addressable Memories with the same number of nonvolatile memory
cells (e.g., memristors), though the input noise immunity of the CrossNet
memories is somewhat lower
Shot noise in frustrated single-electron arrays
We have carried out numerical simulations of shot noise in 2D arrays of
single-electron islands with random background charges. The results show that
in contrast with the 1D arrays, at low currents the current noise is strongly
colored, and its spectral density levels off at very low frequencies. The Fano
factor may be much larger than unity, due to the remnants of
single-electron/hole avalanches. However, even very small thermal fluctuations
reduce the Fano factor below 1 for almost any bias.Comment: 3 pages, 4 figure
Quantum Fluctuations in Josephson Junction Comparators
We have developed a method for calculation of quantum fluctuation effects, in
particular of the uncertainty zone developing at the potential curvature sign
inversion, for a damped harmonic oscillator with arbitrary time dependence of
frequency and for arbitrary temperature, within the Caldeira-Leggett model. The
method has been applied to the calculation of the gray zone width Delta Ix of
Josephson-junction balanced comparators driven by a specially designed
low-impedance RSFQ circuit. The calculated temperature dependence of Delta Ix
in the range 1.5 to 4.2K is in a virtually perfect agreement with experimental
data for Nb-trilayer comparators with critical current densities of 1.0 and 5.5
kA/cm^2, without any fitting parameters.Comment: 4 pages, 4 figures, submitted to Physical Review Letter