Turbulent relaxation after a quench in the Heisenberg model.

We predict the emergence of turbulent scaling in the quench dynamics of the two-dimensional Heisenberg model for a wide range of initial conditions and model parameters. In the isotropic Heisenberg model, we find that the spin-spin correlation function exhibits universal scaling consistent with a turbulent energy cascade. When the spin rotational symmetry is broken with an easy-plane anisotropic exchange, we find a dual cascade of energy and quasiparticles. The scaling is shown to be robust to quantum fluctuations, which tend to inhibit the turbulent relaxation when the spin number $S$ is small. The universal character of the cascade, insensitive to microscopic details or the initial condition, suggests that turbulence in spin systems can be broadly realized in cold atom and solid-state experiments.