Dynamic instabilities and universal relaxation in quantum spin systems

The presence of symmetries and conservation laws can have striking manifestations in the dynamic behavior of interacting quantum systems. I will discuss manifestations of SU(2) symmetry on the universal dynamics of Heisenberg ferromagnets driven out of equilibrium. In particular, I will address the emergence of universal phenomena at two different timescales. Firstly, I will discuss the long-time thermalization behavior of a non-equilibrium incoherent population of magnons, and show that the distribution function can exhibit self-similar behavior in the prethermal regime[1]. Secondly, I will present a new mechanism for dynamic instabilities in a spin spiral state occuring at short timescales, and which originates from the symmetry-constrained quasiparticle interactions[2]. These two seemingly distinct phenomena provide new links between symmetries and universal phenomena occurring at different timescales.
[1] S. Bhattacharyya, JFRN, E. Demler, arXiv:1908.00554
[2] to appear