Fig. 2.

Low-frequency spin conductivity in the noisy XXZ chain. Plot of $\sigma (\omega )$ obtained from MPO simulations at Δ = 12 and for various values of the noise strengths γ. The dashed line corresponds to the predicted intermediate subdiffusive behavior $\sim {\omega }^{1/2}$. Note that the plot starts at $\omega =0.005$, and data for $\gamma =0.05$ are expected to converge to lower values at smaller ω. Moreover, the spectral weights are also redistributed by the noise at higher frequencies (not shown in this plot).