Subdiffusive energy transport in a strongly nonlinear ϕ^{4} lattice

Subdiffusion is argued to be forbidden in a classical homogenous Hamiltonian system due to finiteness of the Poincaré recurrence time. Recently, long-range-interaction-induced subdiffusion has been revealed, which questions the above argument. In this Letter, we study a one-dimensional φ^{4} lattice and present convincing evidence in various aspects that in strong nonlinearity regimes energy transport can be subdiffusive in such a system with neither disorder nor long-range interaction. The calculation of energy diffusivity and conductivity both indicate subdiffusive energy transport and they are in quantitatively consistent with each other. The normal-to-subdiffusive conversion can be understood by match and mismatch between the power spectra and the phonon band of the lattice.