对称晶体中的隐藏角动量环流
Hidden Angular Momentum Loop Currents in Symmetric Crystals
- Boston College（波士顿学院）
- Dartmouth College（达特茅斯学院）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究揭示对称晶体中晶格本身可产生由量子与热涨落维持的隐藏角动量环流，无需电子序或外驱动，拓展了平衡环流物理至晶格动力学。
AI中文摘要：
环流序已被用来解释非常规电子相，其中晶格通常被视为底层集体动力学的被动宿主。在这里，我们表明循环电流可以起源于晶格本身，由量子涨落和热涨落维持。我们发展了一个角动量交换的微观描述，该描述将位点之间的转移与晶体恢复力矩分开，并揭示了在保持对称性的平衡态中循环如何出现。在保持时间反演、反演和四重旋转对称性的二维弹性晶格中，我们发现了相邻元胞上的相反电流环，而每个位点上的平均角动量为零。这些电流由声子真空中的零点涨落维持，并在有限温度下持续存在。我们将其起源追溯到局部对称性降低环境中的定向弹性相互作用，而更高的晶体对称性将由此产生的电流组织成补偿的循环模式。我们的结果将平衡环流物理扩展到晶格动力学，揭示弹性几何可以将涨落组织成持久的角动量循环，而无需电子或磁序、外部驱动或自发对称性破缺。
英文摘要：
Loop-current order has been invoked to explain unconventional electronic phases, with the crystal lattice usually regarded as a passive host for the underlying collective dynamics. Here we show that circulating currents can originate in the lattice itself, sustained by quantum and thermal fluctuations. We develop a microscopic description of angular momentum exchange that separates transfer between sites from crystalline restoring torques and reveals how circulation can emerge in a symmetry-preserving equilibrium state. In a two-dimensional elastic lattice preserving time-reversal, inversion, and fourfold rotational symmetries, we uncover opposite current loops on neighboring plaquettes while the mean angular momentum vanishes at every site. These currents are sustained by zero-point fluctuations in the phonon vacuum and persist at finite temperature. We trace their origin to directional elastic interactions in locally symmetry-lowered environments, with the higher crystal symmetry organizing the resulting currents into a compensated pattern of circulation. Our results extend the physics of equilibrium loop currents to lattice dynamics, revealing that elastic geometry can organize fluctuations into persistent angular momentum circulation without electronic or magnetic order, external driving, or spontaneous symmetry breaking.
