18,115 research outputs found
Resistive switching behavior seen from the energy point of view
The technology of Resistive Switching (RS) devices (memristors) is continuously maturing on its way towards viable commercial establishment. So far, the change of resistance has been identified as a function of the applied pulse characteristics, such as amplitude and duration. However, parameter variability holds back any universal approach based on these two magnitudes, making also difficult even the qualitative comparison between different RS material compounds. On the contrary, there is a relevant magnitude which is much less affected by device variability; the energy. In this direction, we doubt anyone so far has ever wondered 'what is the quantitative effect of the injected energy on the device state?' Interestingly, a first step was made recently towards the definition of performance parameters for this emerging device technology, using as fundamental parameter the energy. In this work, we further elaborate on such ideas, proving experimentally that the 'resistance change per energy unit' (dR/dE) can be considered a significant magnitude in analog operation of bipolar memristors, being a key performance parameter worth of timely disclosure.Peer ReviewedPostprint (author's final draft
Persistent electrical doping of Bi2Sr2CaCu2O8+x mesa structures
Application of a significantly large bias voltage to small Bi2Sr2CaCu2O8+x
mesa structures leads to persistent doping of the mesas. Here we employ this
effect for analysis of the doping dependence of the electronic spectra of
Bi-2212 single crystals by means of intrinsic tunneling spectroscopy. We are
able to controllably and reversibly change the doping state of the same single
crystal from underdoped to overdoped state, without changing its chemical
composition. It is observed that such physical doping is affecting
superconductivity in Bi-2212 similar to chemical doping by oxygen impurities:
with overdoping the critical temperature and the superconducting gap decrease,
with underdoping the c-axis critical current rapidly decreases due to
progressively more incoherent interlayer tunneling and the pseudogap rapidly
increases, indicative for the presence of the critical doping point. We
distinguish two main mechanisms of persistent electric doping: (i) even in
voltage contribution, attributed to a charge transfer effect, and (ii) odd in
voltage contribution, attributed to reordering of oxygen impurities
High frequency electronic ballast provides line frequency lamp current
Most electronic ballasts for fluorescent lamps provide a sinusoidal lamp current at the switching frequency. The high-frequency current flowing through the lamp can generate significant radiated noise, which is unacceptable in noise-sensitive applications, such as fluorescent lights in airplanes. Using shielded enclosures for the lamps may solve the problem, but it is expensive. A discontinuous conduction mode (DCM) electronic ballast topology is presented which drives the lamp with line frequency current, just like a magnetic ballast. However, compared to a magnetic ballast, its weight is substantially reduced due to operation at 40 kHz switching frequency. The topology also ensures unity power factor at the input and stable lamp operation at the output
Dynamics of superconducting nanowires shunted with an external resistor
We present the first study of superconducting nanowires shunted with an
external resistor, geared towards understanding and controlling coherence and
dissipation in nanowires. The dynamics is probed by measuring the evolution of
the V-I characteristics and the distributions of switching and retrapping
currents upon varying the shunt resistor and temperature. Theoretical analysis
of the experiments indicates that as the value of the shunt resistance is
decreased, the dynamics turns more coherent presumably due to stabilization of
phase-slip centers in the wire and furthermore the switching current approaches
the Bardeen's prediction for equilibrium depairing current. By a detailed
comparison between theory and experimental, we make headway into identifying
regimes in which the quasi-one-dimensional wire can effectively be described by
a zero-dimensional circuit model analogous to the RCSJ (resistively and
capacitively shunted Josephson junction) model of Stewart and McCumber. Besides
its fundamental significance, our study has implications for a range of
promising technological applications.Comment: 15 pages, 14 figure
Memristors for the Curious Outsiders
We present both an overview and a perspective of recent experimental advances
and proposed new approaches to performing computation using memristors. A
memristor is a 2-terminal passive component with a dynamic resistance depending
on an internal parameter. We provide an brief historical introduction, as well
as an overview over the physical mechanism that lead to memristive behavior.
This review is meant to guide nonpractitioners in the field of memristive
circuits and their connection to machine learning and neural computation.Comment: Perpective paper for MDPI Technologies; 43 page
- …