Multiple relaxation times in perturbed XXZ chain

Abstract

We numerically study the relaxation of correlation functions in weakly perturbed integrable XXZ chain. The decay of the spin-current and the energy-current correlations at zero magnetization are well described by single, but quite distinct, relaxation rates governed by the square of the perturbation strength $g$. However, at finite magnetization a single correlation function reveals multiple relaxation rates. The result can be understood in terms of multi-scale relaxation scenario, where various relaxation times are linked with various quantities which are conserved in the reference integrable system. On the other hand, the correlations of non-commuting quantities, being conserved at particular anisotropies $\Delta$, decay non-exponentially with characteristic time scale linear in $g$.

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• Spin diffusion in perturbed isotropic Heisenberg spin chain
• From dissipationless to normal diffusion in easy-axis Heisenberg spin chain
• Long-living prethermalization in nearly integrable spin ladders
• Thouless approach in transport in integrable and perturbed easy-axis Heisenberg chains
• Hierarchy of timescales in a disordered spin-$1/2$ XX ladder
• Tunable Hilbert space fragmentation and extended critical regime