Quasistationary states in a quantum dot formed at the edge of a topological insulator by magnetic barriers with finite transparency

A model of quasistationary states is constructed for the one-dimensional edge states propagating along the edge of a two-dimensional topological insulator based on HgTe/CdTe quantum well in the presence of magnetic barriers with finite transparency. The lifetimes of these quasistationary states are found analytically and numerically via different approaches including the solution of the stationary Schrödinger equation with complex energy and the solution of the transmission problem for a double barrier structure. The results can serve as a guide for determining the parameters of magnetic barriers creating the quantum dots where the lifetimes for the broadened discrete levels are long enough for manipulation with their occupation numbers by external fields.

Comparative Analysis of Parallel Hybrid Magnet Memory Machines with Different PM Arrangements

This paper presents a comparative analysis of two parallel hybrid magnet memory machines (PHMMMs) with different permanent magnet (PM) arrangements. The proposed machines are both geometrically characterized by a parallel U-shaped hybrid PM configuration and several q-axis magnetic barriers. The configurations and operating principles of the investigated machines are introduced firstly. The effect of magnet arrangements on the performance of the proposed machines is then evaluated with a simplified magnetic circuit model. Furthermore, the electromagnetic characteristics of the proposed machines are investigated and compared by the finite-element method (FEM). The experiments on one prototype are carried out to validate the FEM results.

Transport properties through graphene with sequence of alternative magnetic barriers and wells in the presence of time-periodic scalar potential

We investigate the electronic transport properties of a graphene sheet under the magnetic barriers and wells through the oscillating scalar potential combined with the static scalar potential barrier having two types of uniform and alternative profiles. We compute the total sideband transmission of the system by additional sidebands at energy, in presence of oscillating potential, $$V_1$$ V 1 , using the transfer-matrix formalism and the Floquet sidebands series. The oscillating potential, generally, suppresses the Klein tunneling and the confinement of the charge carriers. In the absence of $$V_1$$ V 1 , both profiles show the wave vector filtering effect for the carriers by controlling the energy E relative to the potential barrier height, $$V_0$$ V 0 . The $$(N-1)$$ ( N - 1 ) -fold resonance splittings are observed through a region around $$E=V_0$$ E = V 0 with reduction of the transmission. The transmission vanishes in this region upon increasing the number of magnetic blocks N, strength of the magnetic field B in both configurations. We present an estimate relation for the width of the reduction region expressed in terms of E, $$V_0$$ V 0 , B and the angle of incidence of the quasiparticles. We observe, in the second profile, $$(N-1)$$ ( N - 1 ) -fold resonances in the transmission for special values of $$E=V_0$$ E = V 0 with a separation depending on the width of the magnetic blocks. The magnetic field and the width of the magnetic blocks have critical values, where the transmission reduces to zero. All the features observed in the transmission reflect to the conductance. In both configurations, there are some peaks in the conductance corresponding to the resonances of the transmission. The oscillations of the conductance are obtained which was observed in the experimental results. We, also, find the possibility for switching the transport properties of the system by changing the characteristic parameters of the magnetic system.