Retificação de energia e magnetização em cadeias quânticas de spin: análise do modelo XXZ

Abstract

We addressed the issue of energy and magnetization rectification in the quantum one-dimensional open XXZ spin chain driven out of equilibrium by magnetization pumping applied at its boundaries and in the presence of an external magnetic field. We analyzed the effects of the introduction of an inner graded structure in the chain, as well as the effects of a graded magnetic field in the system. We present theoretical results for the fluxes and also exact solutions, obtained by means of numerical computation, for a small chain. We verified that the energy flux exhibits rectification in both the inner graded structure case and the graded magnetic field one, although the magnetization flux exhibits rectification only in the latter situation. With a view to showing that the rectification is not a phenomenon limited to the studied model, we additionally investigated, by means of computational analysis, distinct configurations of the spin chain regarding the chain size, the internal interactions, and the boundary conditions. We found that the same conditions apply to the existence of rectification, except for one situation: with regard to the twisted XY boundary gradients model, the magnetization flux exhibits rectification for a uniform magnetic field as well.