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arXiv 2103.09128cond-mat.str-el
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微扰量子临界Ising链自旋动力学中的级联奇点

Cascade of singularities in the spin dynamics of a perturbed quantum critical Ising chain

Xiao Wang, Haiyuan Zou, Kristóf Hódsági, Márton Kormos, Gábor Takács, Jianda Wu

摘要:

当临界横场伊辛链受到纵场扰动时,在标度极限下出现了一个量子可积模型,该模型具有特殊的$E_{8}$李代数所描述的大质量激发.利用量子$E_{8}$可积模型的相应解析形状因子,系统地研究了扰动量子临界伊辛链的自旋动力学结构因子,其中粒子通道的总能量达到5 $m_1$($m_1$是最轻的$E_{8}$粒子的质量).除了显着的单粒子的动态谱的贡献,每个具有不同质量的双粒子通道被发现表现出边缘奇异性的总质量的阈值和能量的平方根倒数衰减,这是由于在阈值的双粒子态密度的奇异性。由于涉及形状因子的结构的抵消机制,对于具有相等质量的颗粒,奇异性是不存在的。结果表明,动力学结构因子在连续区呈现出一系列具有明显奇异性的碰撞峰,为量子$E_{8}$模型的物质实现提供了坚实的指导.

英文摘要:

When the quantum critical transverse-field Ising chain is perturbed by a longitudinal field, a quantum integrable model emerges in the scaling limit with massive excitations described by the exceptional $E_{8}$ Lie algebra. Using the corresponding analytical form factors of the quantum $E_{8}$ integrable model, we systematically study the spin dynamic structure factor of the perturbed quantum critical Ising chain, where particle channels with total energy up to 5$m_1$ ($m_1$ being the mass of the lightest $E_{8}$ particle) are exhausted. In addition to the significant single-particle contributions to the dynamic spectrum, each two-particle channel with different masses is found to exhibit an edge singularity at the threshold of the total mass and decays with an inverse square root of energy, which is attributed to the singularity of the two-particle density of states at the threshold. The singularity is absent for particles with equal masses due to a cancellation mechanism involving the structure of the form factors. As a consequence, the dynamic structure factor displays a cascade of bumping peaks in the continuum region with clear singular features which can serve as a solid guidance for the material realization of the quantum $E_{8}$ model.

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