Motivated by recent cold-atom experiments, we study the relaxation of spin helices in quantum XXZ chains. The experimentally observed follows scaling laws that are qualitatively different from linear-response transport. We construct a theory such helices, combining generalized hydrodynamics with diffusive corrections and form local density approximation. Although far equilibrium, our hydrodynam...

The use of single molecule magnets in mainstream electronics requires their magnetic moment to be stable over long times. One can achieve such a goal by designing compounds with spin-reversal barriers exceeding room temperature, namely with large uniaxial anisotropies. Such strategy, however, has been defeated by several recent experiments demonstrating under-barrier relaxation at high temperat...

The equations-of-motion for the density matrix are derived in a multiband model to describe the response of semiconductors (bulk or quantum well structures) under optical excitation with arbitrary polarization. The multiband model used, comprising the twofold conduction band and the fourfold topmost valence band (or heavy-and light-hole states), incorporates spin-splitting of the single-particl...