Dissipation and decoherence in quantum magnetic systems

Yi-Hang Nie, J.-Q. Liang, Yunlong Shi +1 more

Михаил Борисович Менский

A. H. Castro Neto, E. Novais, L. Borda +2 more

We discuss the problem of a spin 1/2 impurity immersed in a spin S magnetically ordered background. We show that the problem maps onto a generalization of the dissipative two level system with two independent heat baths, associated with the Goldstone modes of the magnet, that couple to different components of the impurity spin operator. Using analytical perturbative renormalization group methods and accurate numerical renormalization group we show that contrary to other dissipative models there is quantum frustration of decoherence and quasiscaling even in the strong coupling regime. We make predictions for the behavior of the impurity magnetic susceptibility. Our results may also have relevance to quantum computation.

Hans A. De Raedt, V. V. Dobrovitski

Daan van Seters, Tim Ludwig, H. Y. Yuan +1 more

Abstract The coupling between a system and its environment (or bath) always leads to dissipation. We show, however, that a system composed of two subsystems can have a dissipation-free mode, if the bath is shared between the two subsystems. Reading in reverse, a shared bath does not contribute to the dissipation of all modes. As a key example, we consider a simple model for a two-sublattice antiferromagnet, where the environment is modeled by a bath that is shared between the two sublattice magnetizations. In our model, we find that the Néel order parameter is a dissipation-free mode. For antiferromagnets, our results offer an explanation for why the dissipation rate of the Néel vector is typically much lower than that of the average magnetization. In general, our results suggest a way to reduce dissipation (and decoherence) for some modes in composite systems, which could have experimental and technological applications.

V. V. Dobrovitski