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arXiv 1610.05063cond-mat.str-el
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量子临界三维反铁磁体附近的激发能隙标度

Excitation Gap Scaling near Quantum Critical Three-Dimensional Antiferromagnets

Maximilian Lohöfer, Stefan Wessel

摘要:

通过大规模量子蒙特卡罗模拟,我们研究了三维二聚量子反铁磁体双三次晶格中磁激发能隙(三重子能隙)的量子临界标度,并在主要的平均场行为上识别出特征性的乘法对数标度修正。这些发现是符合场论的预测是基于一个有效的描述的量子临界系统的渐近自由场论,它表现出对数衰减的重整化相互作用强度接近量子临界点。此外,使用基于键的单重态光谱,我们确定的振幅(希格斯)反铁磁区域内的模式共振。我们发现一个希格斯质量标度符合场论的预测,涉及到它的一个因素的$\sqrt{2}$相应的三重子间隙的量子无序制度。与低维系统中的情况相反,我们在这个三维耦合二聚体系统中观察到一个不同的信号,从振幅模式也在动态自旋结构因子。观察到希格斯模式共振的宽度与临界附近的希格斯质量成线性比例,这表明对称性破缺相的临界定义良好的激发模式。

英文摘要:

By means of large-scale quantum Monte Carlo simulations, we examine the quantum critical scaling of the magnetic excitation gap (the triplon gap) in a three-dimensional dimerized quantum antiferromagnet, the bicubic lattice, and identify characteristic multiplicative logarithmic scaling corrections atop the leading mean-field behavior. These findings are in accord with field-theoretical predictions that are based on an effective description of the quantum critical system in terms of an asymptotically-free field theory, which exhibits a logarithmic decay of the renormalized interaction strength upon approaching the quantum critical point. Furthermore, using bond-based singlet spectroscopy, we identify the amplitude (Higgs) mode resonance within the antiferromagnetic region. We find a Higgs mass scaling in accord with field-theoretical predictions that relate it by a factor of $\sqrt{2}$ to the corresponding triplon gap in the quantum disordered regime. In contrast to the situation in lower-dimensional systems, we observe in this three-dimensional coupled-dimer system a distinct signal from the amplitude mode also in the dynamical spin structure factor. The width of the Higgs mode resonance is observed to scale linearly with the Higgs mass near criticality, indicative of this critically well-defined excitation mode of the symmetry broken phase.

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