标题： 场诱导的磁振子衰变、磁振子阴影和蜂窝反铁磁体YbBr$_3$中的罗顿激发 显示英文标题

标题： Field-Induced Magnon Decay, Magnon Shadows, and Roton Excitations in the Honeycomb Antiferromagnet YbBr$_3$

摘要： 尽管在磁性材料中寻找量子多体现象的研究主要集中在高度受挫的系统上，但即使是没有受挫的量子磁体在其自旋激发谱中也表现出多种非常规现象。 YbBr$_3$是蜂窝晶格上$S = 1/2$反铁磁海森堡模型的一个优秀实现，在所有施加的磁场直到饱和的情况下，我们使用非极化和极化中子进行了详细光谱实验。 我们观察到广泛的激发连续谱，这导致在较高磁场下单磁子的强烈重整化和衰减，而相干特征包括场诱导的单磁子“阴影”以及罗顿-like 激发的显著出现。 为了指导和解释我们的实验，我们通过圆柱矩阵乘积态方法进行了系统计算，这些计算与中子散射数据有定量的一致性，并且在没有磁性受挫的情况下，为强量子涨落的谱特征提供了定性的基准。 显示英文摘要

摘要： Although the search for quantum many-body phenomena in magnetic materials has a strong focus on highly frustrated systems, even unfrustrated quantum magnets show a multitude of unconventional phenomena in their spin excitation spectra. YbBr$_3$ is an excellent realization of the $S = 1/2$ antiferromagnetic Heisenberg model on the honeycomb lattice, and we have performed detailed spectroscopic experiments with both unpolarized and polarized neutrons at all applied magnetic fields up to saturation. We observe extensive excitation continua, which cause strong renormalization and the decay of single magnons at higher fields, while coherent features include field-induced ``shadows'' of the single magnons and the spectacular emergence of a roton-like excitation. To guide and interpret our experiments, we performed systematic calculations by the method of cylinder matrix-product states that provide quantitative agreement with the neutron scattering data and a qualitative benchmark for the spectral signatures of strong quantum fluctuations even in the absence of magnetic frustration.