Thermal conductivity in 1d: Disorder-induced transition from anomalous to normal scaling

It is well known that the contribution of harmonic phonons to the thermal conductivity of 1D systems diverges with the harmonic chain length L. Within various one-dimensional models containing disorder it was shown that the thermal conductivity scales as $\sqrt{L}$ under certain boundary conditions. Here we show that when the chain is weakly coupled to the heat reservoirs and there is strong disorder this scaling can be violated. We find a weaker power-law dependence on L, and show that for sufficiently strong disorder the thermal conductivity ceases to be anomalous – it does not depend on L and hence obeys Fourier's law. This is despite both density of states and the diverging localization length scaling anomalously. Surprisingly, in this strong disorder regime two anomalously scaling quantities cancel each other to recover Fourier's law of heat transport