Anomalous cross-field diffusion in a magnetic trap

We numerically simulated the diffusion of a charged Brownian particle confined to a plane under the action of an orthogonal magnetic field with intensity depending on the distance from a center. Despite its apparent simplicity, this system exhibits anomalous diffusion. For positive field gradients, radial and angular dynamics are asymptotically subdiffusive, with exponents given by simple analytical expressions. In contrast, when driven by a weakly decaying field, the particle attains normal diffusion only after exceedingly long superdiffusive transients. These mechanisms can be related to Bohm diffusion in magnetized plasmas

Mesoscopic resistive switch: non-volatility, hysteresis and negative differential resistance

We show how a simple model nanoswitch can perform as a memory resistor. Its resistance is determined by electron tunneling through a nanoparticle diffusing around one or more potential minima located between the electrodes in the presence of Joule’s heat dissipation. In the case of a single potential minimum, we observe hysteresis of the resistance at finite applied currents and negative differential resistance. For two (or more) minima the switching mechanism is non-volatile, meaning that the memristor can switch to a resistive state of choice and stay there. Moreover, the noise spectra of the switch exhibit 1/f2 → 1/f crossover, in agreement with recent experimental results

Synchronization of geometric stochastic resonance by a bi-harmonic drive

When simulating the Langevin dynamics of an elongated particle simultaneously driven by a low- and a high-frequency harmonic drive across a porous membrane, we observed an unusual manifestation of stochastic resonance, with the particle oscillating out of phase with the low-frequency drive. This effect is related to the absolute negative mobility the same particle would exhibit, when setting the low frequency to zero. Here as well the magnitude of the out-of-phase stochastic resonance depends on how the combined action of driving forces and noise fluctuations impacts the particle orientation and, as such, is very sensitive to the particle shape