美国莱斯大学Hanyu Zhu团队报道了稀土卤化物中手性声子产生的大有效磁场。相关研究成果于2023年11月10日发表在《科学》。

时间反转对称性（TRS）对材料的光学、磁性、拓扑和输运特性至关重要。手性声子的特征是原子围绕其平衡位置单向旋转，产生破坏TRS的动态晶格结构。

该文中，研究人员报道了由圆偏振太赫兹光脉冲驱动的相干手性声子，以类似于1特斯拉量级的准静态磁场的方式偏振氟化铈中的顺磁自旋。通过时间分辨法拉第旋转和克尔椭圆率，发现瞬态磁化仅由与声子共振的脉冲激发，与声子的角动量成比例，并在低温下随磁化率增长。

这一观察结果在数量上与自旋-声子耦合模型一致，并可能为研究超快磁性、高能自旋电子学和TRS断裂的物质的非平衡相开辟新的途径。

附：英文原文

Title: Large effective magnetic fields from chiral phonons in rare-earth halides

Author: Jiaming Luo, Tong Lin, Junjie Zhang, Xiaotong Chen, Elizabeth R. Blackert, Rui Xu, Boris I. Yakobson, Hanyu Zhu

Issue&Volume: 2023-11-10

Abstract: Time-reversal symmetry (TRS) is pivotal for materials’ optical, magnetic, topological, and transport properties. Chiral phonons, characterized by atoms rotating unidirectionally around their equilibrium positions, generate dynamic lattice structures that break TRS. Here, we report that coherent chiral phonons, driven by circularly polarized terahertz light pulses, polarize the paramagnetic spins in cerium fluoride in a manner similar to that of a quasi-static magnetic field on the order of 1 tesla. Through time-resolved Faraday rotation and Kerr ellipticity, we found that the transient magnetization is only excited by pulses resonant with phonons, proportional to the angular momentum of the phonons, and growing with magnetic susceptibility at cryogenic temperatures. The observation quantitatively agrees with our spin-phonon coupling model and may enable new routes to investigating ultrafast magnetism, energy-efficient spintronics, and nonequilibrium phases of matter with broken TRS.

DOI: adi9601

Source: https://www.science.org/doi/10.1126/science.adi9601