## SciPost Submission Page

# Domain wall problem in the quantum XXZ chain and semiclassical behavior close to the isotropic point

### by Grégoire Misguich, Nicolas Pavloff, Vincent Pasquier

### Submission summary

As Contributors: | Grégoire Misguich · Nicolas Pavloff |

Arxiv Link: | https://arxiv.org/abs/1905.08756v1 |

Date submitted: | 2019-05-22 |

Submitted by: | Misguich, Grégoire |

Submitted to: | SciPost Physics |

Domain(s): | Theor. & Comp. |

Subject area: | Condensed Matter Physics - Theory |

### Abstract

We study the dynamics of a spin-1/2 XXZ chain which is initially prepared in a domain-wall state. We compare the results of time-dependent Density Matrix Renormalization Group simulations with those of an effective description in terms of a classical anisotropic Landau-Lifshitz (LL) equation. Numerous quantities are analyzed: magnetization (x, y and z components), energy density, energy current, but also some spin-spin correlation functions or entanglement entropy in the quantum chain. Without any adjustable parameter a quantitative agreement is observed between the quantum and the LL problems in the long time limit, when the models are close to the isotropic point. This is explained as a consequence of energy conservation. At the isotropic point the mapping between the LL equation and the nonlinear Schrödinger equation is used to construct a variational solution capturing several aspects of the problem.