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Here, a method to suppress resonant multipaction in microwave systems is proposed in which the radio frequency system's metal plates are patterned with a three-dimensional periodic ripple profile in which each unit is two orders smaller than the radio frequency wavelength. The multipaction-inhibiting mechanism was studied analytically and with a particle-in-cell simulation. The analytical and three-dimensional electromagnetic simulated field distribution of the rotationally symmetric surface structures shows the evanescent E-field characteristics in the ripple valleys, which increase the electron staid time and the temporal dispersion of the secondary electron generation, as well as causing the electrons to deviate from the resonant phase that causes multipaction. [ABSTRACT FROM AUTHOR]

We propose a pure-spin-current generator based on a single level quantum dot (QD) device subjected to time-dependent magnetic fields. Under low temperature and high magnetic fields, the spin-dependent Seebeck coefficient in the transition regime is rapidly enhanced by several orders of magnitude larger than that in the steady regime. This fact is attributed to a delay effect of the electron transmission probability with respect to the split of the QD energy level. When a temperature gradient is applied across the device, the pure spin current emerges. The findings here suggest a feasible way of enhancing thermospin effects and generating the pure spin current by time-dependent external fields. [ABSTRACT FROM AUTHOR]

A finite-size effect leads to more electrons to occupy high-energy states in a graphene nanoribbon. Therefore, the thermionic-emission (TE) current density of a metal/graphene nanoribbon changes with its width when the graphene nanoribbon is a semiconductor. This letter demonstrates that the TE current density increases rapidly with the decreasing width of the graphene nanoribbon. It is also found that the finite-size effect TE current density is more significant at low temperatures. [ABSTRACT FROM AUTHOR]