Padmanabhan Hari, Poore Maxwell, Kim Peter K, Koocher Nathan Z, Stoica Vladimir A, Puggioni Danilo, Hugo Wang Huaiyu, Shen Xiaozhe, Reid Alexander H, Gu Mingqiang, Wetherington Maxwell, Lee Seng Huat, Schaller Richard D, Mao Zhiqiang, Lindenberg Aaron M, Wang Xijie, Rondinelli James M, Averitt Richard D, Gopalan Venkatraman
Materials Research Institute and Department of Materials Science & Engineering, Pennsylvania State University, University Park, PA, USA.
Department of Physics, Harvard University, Cambridge, MA, USA.
Nat Commun. 2022 Apr 8;13(1):1929. doi: 10.1038/s41467-022-29545-5.
The emergence of magnetism in quantum materials creates a platform to realize spin-based applications in spintronics, magnetic memory, and quantum information science. A key to unlocking new functionalities in these materials is the discovery of tunable coupling between spins and other microscopic degrees of freedom. We present evidence for interlayer magnetophononic coupling in the layered magnetic topological insulator MnBiTe. Employing magneto-Raman spectroscopy, we observe anomalies in phonon scattering intensities across magnetic field-driven phase transitions, despite the absence of discernible static structural changes. This behavior is a consequence of a magnetophononic wave-mixing process that allows for the excitation of zone-boundary phonons that are otherwise 'forbidden' by momentum conservation. Our microscopic model based on density functional theory calculations reveals that this phenomenon can be attributed to phonons modulating the interlayer exchange coupling. Moreover, signatures of magnetophononic coupling are also observed in the time domain through the ultrafast excitation and detection of coherent phonons across magnetic transitions. In light of the intimate connection between magnetism and topology in MnBiTe, the magnetophononic coupling represents an important step towards coherent on-demand manipulation of magnetic topological phases.
量子材料中磁性的出现为在自旋电子学、磁存储器和量子信息科学中实现基于自旋的应用创造了一个平台。在这些材料中解锁新功能的关键是发现自旋与其他微观自由度之间的可调耦合。我们给出了层状磁性拓扑绝缘体MnBiTe中层间磁声子耦合的证据。利用磁拉曼光谱，我们观察到在磁场驱动的相变过程中声子散射强度出现异常，尽管没有明显的静态结构变化。这种行为是磁声子波混合过程的结果，该过程允许激发那些否则会因动量守恒而“被禁止”的边界声子。我们基于密度泛函理论计算的微观模型表明，这种现象可归因于声子对层间交换耦合的调制。此外，通过超快激发和检测磁跃迁过程中的相干声子，在时域中也观察到了磁声子耦合的特征。鉴于MnBiTe中磁性与拓扑之间的紧密联系，磁声子耦合代表了朝着对磁拓扑相进行相干按需操纵迈出的重要一步。
