Amplitude Mode in Quantum Magnets via Dimensional Crossover
Amplitude Mode in Quantum Magnets via Dimensional Crossover
复制标题
通过维度交叉实现量子磁体的振幅模式
DOI：
10.1103/physrevlett.126.227201
复制
发表时间：
2021
影响因子：
8.6
通讯作者：
Meng Zi Yang
中科院分区：
文献类型：
--
作者：
Zhou Chengkang;Yan Zheng;Wu Han-Qing;Sun Kai;Starykh Oleg A.;Meng Zi Yang
我们研究了连续自发对称破缺相变中与序参量纵向涨落相关的振幅（Higgs）模。在量子磁体中，由于振幅模式快速衰减为低能戈德斯通激发，直接观察这种模式是一项具有挑战性的任务。通过专注于准一维的几何形状，我们绕过困难和调查的振幅模式的弱耦合自旋链系统的帮助下，量子Monte Carlo模拟，随机解析延拓，链平均场的方法结合映射到场论正弦戈登模型。观察到振幅模式出现在纵向自旋磁化率的存在下，一个弱的破缺交错场。在较高的维度，单线键模式，振幅模式的常规措施，发现出现在一个低于振幅模式的频率。我们确定这两个激发与第二（第一）呼吸的正弦戈登理论，相应地。与高维系统相比，振幅和键级波动被发现进行显着的光谱重量在准一维极限。
We investigate the amplitude (Higgs) mode associated with longitudinal fluctuations of the order parameter at the continuous spontaneous symmetry breaking phase transition. In quantum magnets, due to the fast decay of the amplitude mode into low-energy Goldstone excitations, direct observation of this mode represents a challenging task. By focusing on a quasi-one-dimensional geometry, we circumvent the difficulty and investigate the amplitude mode in a system of weakly coupled spin chains with the help of quantum Monte Carlo simulations, stochastic analytic continuation, and a chain-mean field approach combined with a mapping to the field-theoretic sine-Gordon model. The amplitude mode is observed to emerge in the longitudinal spin susceptibility in the presence of a weak symmetry-breaking staggered field. A conventional measure of the amplitude mode in higher dimensions, the singlet bond mode, is found to appear at a lower than the amplitude mode frequency. We identify these two excitations with the second (first) breather of the sine-Gordon theory, correspondingly. In contrast to higher-dimensional systems, the amplitude and bond order fluctuations are found to carry significant spectral weight in the quasi-1D limit.