Research: Domain Wall Dynamics in Classical Spin Chains

The Heisenberg spin chain is a fundamental model of magnetism.  Even after many decades of investigation, both the classical and quantum versions of this model continue to present new surprises.

McRoberts et al. examined the dynamics of a classical anisotropic spin chain with a sharp domain wall initial condition. The resulting dynamics is rich, and displays an intriguing co-existence of linear and non-linear physics. For easy-plane anisotropy, the domain wall splits into two ballistically counter-propagating ones. The propagation and spreading of domain walls can be well-described by linear spin-wave theory, while, simultaneously, stable (non-broadening) topological solitons are emitted for a wide range of easy-plane anisotropies.   The whole easy-plane regime displays a subdiffusive broadening of the domain wall widths, with exponent 1/3. This behavior is in stark contrast to the quantum case, where broadening is typically diffusive (exponent 1/2), and subdiffusive broadening is seen solely at the non-interacting (XX) point.

A. J. McRoberts, T. Bilitewski, M. Haque, R. Moessner,
Domain Wall Dynamics in Classical Spin Chains: Free Propagation, Subdiffusive Spreading, and Soliton Emission,
Phys. Rev. Lett. 132, 057202 (2024) (arXiv)