Constraining quantum critical dynamics: 2+1D Ising model and beyond
William Witczak-Krempa
备注：
4+7 pages, 1+2 figs. v3: Paper simplified & reorganized to improve clarity. New appendix on analytic continuation. Minor corrections & added references
Quantum critical (QC) phase transitions generally lead to the absence of quasiparticles. The resulting correlated quantum fluid, when thermally excited, displays rich universal dynamics. We establish non-perturbative constraints on the linear-response dynamics of conformal QC systems at finite temperature, in spatial dimensions above one. Specifically, we analyze the large frequency/momentum asymptotics of observables, which we use to derive powerful sum rules and inequalities. The general results are applied to the O(N) Wilson-Fisher fixed point, describing the QC Ising model when N = 1. We focus on the order parameter and scalar susceptibilities, and the dynamical shear viscosity. Connections to simulations, experiments and gauge theories are made.
Magnetization beyond the Ising limit of Ho$_2$Ti$_2$O$_7$
我们报告说，在烧绿石氧化物的局部伊辛各向异性-实现自旋冰状态的关键要求-可以通过高磁场打破。对于已经确定的经典自旋-冰化合物Ho $_2$ Ti $_2$ O $_7$的情况，磁化强度超过使用高达120 T的超高场的伊辛极限的依赖于角度的饱和值。然而，即使在这种极端的磁场下也不能实现完全饱和。晶体电场计算表明，四个离子位置中的两个的水平交叉导致在55和100 T的磁化步骤。此外，我们表明，通过使用的自旋弛豫时间的范围内的场扫描速率的自旋系统的动力学可以探测。只有在25 ns/T时，磁化率的新峰值出现在2 T附近。我们认为，这标志着自旋冰和极化相关性之间的交叉。
Strong-to-Weak Spontaneous Symmetry Breaking in a $(2+1)$D Transverse-Field Ising Model under Decoherence
Westlake University（西湖大学）；Westlake Institute for Advanced Study（西湖高等研究院）；Fudan University（复旦大学）；University of Tokyo（东京大学）；The Pennsylvania State University（宾夕法尼亚州立大学）
