Real-time dynamics of angular momentum transfer from spin to acoustic chiral phonon in oxide heterostructures

IF 38.1 1区材料科学 Q1 MATERIALS SCIENCE, MULTIDISCIPLINARY

Nature nanotechnology Pub Date : 2024-07-12 DOI:10.1038/s41565-024-01719-w

In Hyeok Choi, Seung Gyo Jeong, Sehwan Song, Sungkyun Park, Dong Bin Shin, Woo Seok Choi, Jong Seok Lee

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Abstract

Chiral phonons have recently been explored as a novel degree of freedom in quantum materials. The angular momentum carried by these quasiparticles is generated by the breaking of chiral degeneracy of phonons, owing to the chiral lattice structure or the rotational motion of ions of the material. In ferromagnets, a mechanism for generating non-equilibrium chiral phonons has been suggested, but their temporal evolution, which obeys Bose–Einstein statistics, remains unclear. Here we report the real-time dynamics of thermalized chiral phonons in an artificial superlattice composed of ferromagnetic metallic SrRuO3 and non-magnetic insulating SrTiO3. Following the photo-induced ultrafast demagnetization in the SrRuO3 layer, we observed the appearance of a magneto-optic signal in the superlattice, which is absent in the SrRuO3 single films. This magneto-optic signal exhibits thermally driven dynamic properties and a clear correlation with the thickness of the non-magnetic SrTiO3 layer, implying that it originates from thermalized chiral phonons. We use numerical calculations considering the magneto-elastic coupling in SrRuO3 to validate our experimental observations and the angular momentum transfer mechanism between the lattice and spin systems in ferromagnetic systems and also to the non-magnetic system. Not only electrons but also phonons can transport angular momentum in solids. Now, in an artificial superlattice, ultrafast demagnetization induces transfer of angular momentum from the spin system to the lattice.

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氧化物异质结构中从自旋到声学手性声子的角动量实时动态转移

手性声子作为量子材料中的一种新的自由度，最近得到了探索。由于材料的手性晶格结构或离子的旋转运动，声子的手性退行性被打破，从而产生了这些准粒子所携带的角动量。在铁磁体中，已经提出了一种产生非平衡手性声子的机制，但其服从玻色-爱因斯坦统计的时间演化仍不清楚。在这里，我们报告了由铁磁性金属 SrRuO3 和非磁性绝缘 SrTiO3 组成的人工超晶格中热化手性声子的实时动态。在 SrRuO3 层中发生光诱导超快消磁后，我们观察到超晶格中出现了磁光信号，而 SrRuO3 单层薄膜中则没有这种信号。这种磁光信号具有热驱动的动态特性，并与无磁性 SrTiO3 层的厚度明显相关，这意味着它源自热化手性声子。我们利用考虑到 SrRuO3 中磁弹性耦合的数值计算来验证我们的实验观察结果，以及铁磁系统中晶格和自旋系统之间以及与非磁性系统之间的角动量传递机制。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Nature nanotechnology 工程技术-材料科学：综合

CiteScore

59.70

自引率

0.80%

发文量

196

审稿时长

4-8 weeks

期刊介绍： Nature Nanotechnology is a prestigious journal that publishes high-quality papers in various areas of nanoscience and nanotechnology. The journal focuses on the design, characterization, and production of structures, devices, and systems that manipulate and control materials at atomic, molecular, and macromolecular scales. It encompasses both bottom-up and top-down approaches, as well as their combinations. Furthermore, Nature Nanotechnology fosters the exchange of ideas among researchers from diverse disciplines such as chemistry, physics, material science, biomedical research, engineering, and more. It promotes collaboration at the forefront of this multidisciplinary field. The journal covers a wide range of topics, from fundamental research in physics, chemistry, and biology, including computational work and simulations, to the development of innovative devices and technologies for various industrial sectors such as information technology, medicine, manufacturing, high-performance materials, energy, and environmental technologies. It includes coverage of organic, inorganic, and hybrid materials.