RESUMO
Recently developed diffusive memristors have gathered a large amount of research attention due to their unique property to exhibit a variety of spiking regimes reminiscent to that found in biological cells, which creates a great potential for their application in neuromorphic systems of artificial intelligence and unconventional computing. These devices are known to produce a huge range of interesting phenomena through the interplay of regular, chaotic, and stochastic behavior. However, the character of these interplays as well as the instabilities responsible for different dynamical regimes are still poorly studied because of the difficulties in analyzing the complex stochastic dynamics of the memristive devices. In this paper, we introduce a new deterministic model justified from the Fokker-Planck description to capture the noise-driven dynamics that noise has been known to produce in the diffusive memristor. This allows us to apply bifurcation theory to reveal the instabilities and the description of the transition between the dynamical regimes.
RESUMO
Reversible bipolar nanoswitches that can be set and read electronically in a solid-state two-terminal device are very promising for applications. We have performed molecular dynamics simulations that mimic systems with oxygen vacancies interacting via realistic potentials and driven by an external bias voltage. The competing short- and long-range interactions among charged mobile vacancies lead to density fluctuations and short-range ordering, while illustrating some aspects of observed experimental behavior, such as memristor polarity inversion. The simulations show that the 'localized conductive filaments' and 'uniform push/pull' models for memristive switching are actually two extremes of the one stochastic mechanism.
RESUMO
The vortex-lattice melting transition in Bi(2)Sr(2)CaCu(2)O(8 + delta) single crystals was studied using in-plane resistivity measurements in magnetic fields tilted away from the c axis to the ab plane. In order to avoid the surface barrier effect which hinders the melting transition in the conventional transport measurements, we used the Corbino geometry of electric contacts. The complete H(c) - H(ab) phase diagram of the melting transition in Bi(2)Sr(2)CaCu(2)O(8 + delta) is obtained for the first time. The c-axis melting field component H(c)(melt) exhibits the novel, stepwise dependence on the in-plane magnetic fields H(ab) which is discussed on the basis of the crossing vortex-lattice structure. The peculiar resistance behavior observed near the ab plane suggests the change of phase transition character from first to second order.
