该研究团队考虑了一个位于三维烧绿石晶格上的自旋系统，其中出现的规范场不仅描述了零温度下的自旋液体行为，而且关键性地决定了系统的温度演化，不同的规范场在不同的温度范围内产生了不同的自旋液体相。
研究人员首先关注经典自旋，在中间温度范围内，系统表现出一种不寻常的现象，即矢量规范场和张量规范场共存，其中前者在经典自旋冰系统中已知，而后者则与分形子准粒子相关，这是一种具有受限移动性的特殊类型的激发。在冷却过程中，系统过渡到低温相，其中熵选择机制使与张量规范场相关的自由度减少，使系统呈现出自旋冰状。
研究人员进一步提供了数值证据，表明在相应的量子模型中，具有共存的矢量规范场和张量规范场的自旋液体在自旋相互作用的参数空间中具有有限的稳定性窗口，直至零温度。最后，研究人员讨论了这一发现对非克拉默斯磁性烧绿石材料的意义。
据悉，规范理论是强大的理论物理学工具，能够将复杂现象归结为简单原理，并应用于高能物理学和凝聚态物理学。在后者的背景下，规范理论在捕获自旋液体中复杂的自旋相关性方面越来越受欢迎，自旋液体是一种奇特的物质状态，即使在绝对零度下，量子自旋的动力学也永不停歇。
附：英文原文
Title: Competing gauge fields and entropically driven spin liquid to spin liquid transition in non-Kramers pyrochlores
Author: Lozano-Gómez, Daniel, Noculak, Vincent, Oitmaa, Jaan, Singh, Rajiv R. P., Iqbal, Yasir, Reuther, Johannes, Gingras, Michel J. P.
Issue&Volume: 2024-8-28
Abstract: Gauge theories are powerful theoretical physics tools that allow complex phenomena to be reduced to simple principles and are used in both high-energy and condensed matter physics. In the latter context, gauge theories are becoming increasingly popular for capturing the intricate spin correlations in spin liquids, exotic states of matter in which the dynamics of quantum spins never ceases, even at absolute zero temperature. We consider a spin system on a three-dimensional pyrochlore lattice where emergent gauge fields not only describe the spin liquid behavior at zero temperature but crucially determine the system’s temperature evolution, with distinct gauge fields giving rise to different spin liquid phases in separate temperature regimes. Focusing first on classical spins, in an intermediate temperature regime, the system shows an unusual coexistence of emergent vector and tensor gauge fields where the former is known from classical spin ice systems while the latter has been associated with fractonic quasiparticles, a peculiar type of excitation with restricted mobility. Upon cooling, the system transitions into a low-temperature phase where an entropic selection mechanism depopulates the degrees of freedom associated with the tensor gauge field, rendering the system spin-ice-like. We further provide numerical evidence that in the corresponding quantum model, a spin liquid with coexisting vector and tensor gauge fields has a finite window of stability in the parameter space of spin interactions down to zero temperature. Finally, we discuss the relevance of our findings for non-Kramers magnetic pyrochlore materials.
DOI: 10.1073/pnas.2403487121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2403487121