Landau-Zener transition of a two-level system driven by spin chains near their critical points
The Landau-Zener (LZ) transition of a two-level system coupling to spin chains near their critical points is studied in this paper. Two kinds of spin chains, the Ising spin chain and XY spin chain, are considered. We calculate and analyze the effects of system-chain coupling on the LZ transition. A relation between the LZ transition and the critical points of the spin chain is established. These results suggest that LZ transitions may serve as the witnesses of criticality of the spin chain. This may provide a new way to study quantum phase transitions as well as LZ transitions.
The first problem in our third millennium is energy. For this raison, we try to find a new solution to develop different ways of distribution and energy use. This article presents the design of a sliding mode controller using sliding mode observation technique which aims to simplify the control procedure. For ameliorating the quality of the energy transferred from the power supply to the load, and minimizing the harmful effects of the harmonics generated by nonlinear load. The virtual grid flux vector estimated in the sliding-mode observer yields robustness against the line voltage distortions. We propose a new multi-function converter as an efficient solution to improve the power quality. The good dynamic and static performance under the proposed control strategy is verified by simulation and experiment .