Weakly interacting quasiparticles play a central role in the low-energy description of many phases of quantum matter. At higher energies, however, quasiparticles cease to be well defined in generic many-body systems owing to a proliferation of decay channels. In this review, we discuss the phenomenon of quantum many-body scars, which can give rise to certain species of stable quasiparticles throughout the energy spectrum. This goes along with a set of unusual nonequilibrium phenomena including many-body revivals and nonthermal stationary states. We provide a pedagogical exposition of this physics via a simple yet comprehensive example, that of a spin-1 XY model. We place our discussion in the broader context of symmetry-based constructions of many-body scar states, projector embeddings, and Hilbert space fragmentation. We conclude with a summary of experimental progress and theoretical puzzles.

中文翻译：

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量子多体疤痕：准粒子视角


弱相互作用准粒子在量子物质许多相的低能描述中发挥着核心作用。然而，在较高能量下，由于衰变通道的扩散，准粒子在通用多体系统中不再被明确定义。在这篇综述中，我们讨论了量子多体疤痕现象，它可以在整个能谱中产生某些稳定的准粒子。这伴随着一系列不寻常的非平衡现象，包括多体复兴和非热静止状态。我们通过一个简单而全面的例子（自旋 1 XY 模型）对该物理现象进行了教学阐述。我们将我们的讨论放在更广泛的背景下，即基于对称的多体疤痕状态、投影嵌入和希尔伯特空间碎片的构造。最后我们总结了实验进展和理论难题。