近日，美国德克萨斯大学奥斯汀分校的Xiaoqin Li及其研究小组与德克萨斯理工大学的Rui He等人合作并取得一项新进展。经过不懈努力，他们发现量子磁体中自旋轨道激子诱导的声子手性。相关研究成果已于2024年3月8日在国际知名学术期刊《美国科学院院刊》上发表。

该研究团队报道了在CTO中由强自旋轨道耦合、大晶体场分裂和三角畸变联合产生的声子特性。具体来说，声子与SOE之间的相互作用赋予了两种E_g声子模式手性，并导致在磁拉曼光谱中观察到的大声子磁矩。强磁声子效应是由于声子和SOE的能量接近而产生的杂化效应。

虽然手性声子在某些材料中与电子拓扑有关，但这项研究工作表明，通过探索与拓扑玻色子耦合的手性声子可能会产生机会。

据悉，在相关材料中，电荷、自旋、晶格和轨道自由度的相互作用常常导致丰富和奇异的性质。近年来的研究为相关材料中的玻色子集体激发带来了新的视角。例如，非弹性中子散射实验揭示了，量子磁体CoTiO₃ (CTO)中磁振子和自旋轨道激子(SOEs)的非平凡带拓扑结构。

附：英文原文

Title: Spin–orbit exciton–induced phonon chirality in a quantum magnet

Author: Lujan, David, Choe, Jeongheon, Chaudhary, Swati, Ye, Gaihua, Nnokwe, Cynthia, Rodriguez-Vega, Martin, He, Jiaming, Gao, Frank Y., Nunley, T. Nathan, Baldini, Edoardo, Zhou, Jianshi, Fiete, Gregory A., He, Rui, Li, Xiaoqin

Issue&Volume: 2024-3-8

Abstract: The interplay of charge, spin, lattice, and orbital degrees of freedom in correlated materials often leads to rich and exotic properties. Recent studies have brought new perspectives to bosonic collective excitations in correlated materials. For example, inelastic neutron scattering experiments revealed non-trivial band topology for magnons and spin–orbit excitons (SOEs) in a quantum magnet CoTiO₃ (CTO). Here, we report phonon properties resulting from a combination of strong spin–orbit coupling, large crystal field splitting, and trigonal distortion in CTO. Specifically, the interaction between SOEs and phonons endows chirality to two E_g phonon modes and leads to large phonon magnetic moments observed in magneto-Raman spectra. The remarkably strong magneto-phononic effect originates from the hybridization of SOEs and phonons due to their close energy proximity. While chiral phonons have been associated with electronic topology in some materials, our work suggests opportunities may arise by exploring chiral phonons coupled to topological bosons.

DOI: 10.1073/pnas.2304360121

Source: https://www.pnas.org/doi/abs/10.1073/pnas.2304360121