原子ダンスが磁石を生み出す:希土類ハロゲン化物のキラルフォノンを利用した量子効果の研究(Atomic dance gives rise to a magnet:Rice study leverages chiral phonons for transformative quantum effect)

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2023-11-09 ライス大学

原子ダンスが磁石を生み出す:希土類ハロゲン化物のキラルフォノンを利用した量子効果の研究(Atomic dance gives rise to a magnet:Rice study leverages chiral phonons for transformative quantum effect)

◆ライス大学の研究者は、希土類結晶に超高速の光パルスを照射すると、その原子がコークスクリュー状の振動(キラルフォノン)になり、一時的に電子のスピンを整列させ、結晶を磁石化できることを発見しました。
◆この効果は時間的には短命ですが、光パルスの持続時間をはるかに上回る時間にわたってスピンを整列させる力があります。この新しい現象により、物質の電気、光学、磁気特性への影響を定量的に測定し、スピン-フォノン結合と呼ばれる興味深い現象に対する理解が深まりました。

<関連情報>

希土類ハロゲン化物中のキラルフォノンによる大きな有効磁場 Large effective magnetic fields from chiral phonons in rare-earth halides

Jiaming Luo,Tong Lin,Junjie Zhang,Xiaotong Chen,Elizabeth R. Blackert,Rui Xu,Boris I. Yakobson,and Hanyu Zhu
Science  Published:9 Nov 2023
DOI:https://doi.org/10.1126/science.adi9601

Editor’s summary

The manipulation and control of the optoelectronic properties of a material finds application across a range of fields. However, doing so by applying electric or magnetic fields can be slow and not always practical. Luo et al. have shown that chiral phonons driven by ultrafast pulses of circularly polarized terahertz radiation can induce magnetic fields on the order of one tesla in the rare earth trihalide cerium fluoride (see the Perspective by Kaindl). Such control of spin-phonon coupling provides a route to on-demand ultrafast, large magnetic fields on an atomic scale that would be useful for both fundamental materials science and the development of energy-efficient spintronic devices. —Ian S. Osborne

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.

1700応用理学一般
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