Decay of spin helices in XXZ quantum spin chains with single-ion anisotropy

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Abstract
Long-lived spin-helix states facilitate the study of nonequilibrium dynamics in quantum magnets. We consider the decay of transverse spin helices in antiferromagnetic spin- S XXZ chains with single-ion anisostropy. The spin-helix decay is observable in the time evolution of the local magnetization that we calculate numerically for the system in the thermodynamic limit using infinite time-evolving block decimation simulations. Although the single-ion anisotropy prevents helix states from being eigenstates of the Hamiltonian, they still can be long-lived for appropriately chosen wave numbers. In the case of easy-axis exchange anisotropy, the single-ion anisotropy may even stabilize the helices. Within a spin-wave approximation, we obtain a condition giving an estimate for the most stable wave number Q that agrees qualitatively with our numerical results.
Funding Information
  • Friedrich-Alexander-Universität Erlangen-Nürnberg
  • Deutsche Forschungsgemeinschaft

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