近日，美国麻省理工学院的Nuh Gedik及其研究团队取得一项新进展。他们实现了FePS₃中临界点附近的太赫兹场诱导亚稳磁化。相关研究成果已于2024年12月18日在国际权威学术期刊《自然》上发表。

本研究利用强烈的太赫兹脉冲，在范德华反铁磁体FePS₃中诱导出了一种具有超长寿命（超过2.5毫秒）的亚稳磁化状态。随着温度接近反铁磁转变点，这种亚稳状态变得越来越稳定，表明临界序参量波动在延长其寿命方面起着重要作用。

通过结合第一性原理计算、经典蒙特卡洛模拟和自旋动力学模拟，研究人员发现特定声子模式的位移以一种，有利于在尼尔温度附近形成有限磁化基态的方式调制了交换耦合。这一分析还阐明了主导反铁磁序的临界波动，如何放大新磁态的强度和寿命。

本研究的发现展示了利用太赫兹光通过非热途径，有效操控层状磁体的磁基态，并确定了在临界点附近、序参量波动增强的区域，是寻找亚稳隐藏量子态的有前景的领域。

据悉，利用光来控制量子材料的功能特性已成为凝聚态物理学的前沿领域，这一领域已经发现了多种光诱导的物质相，如超导性、铁电性、磁性和电荷密度波。然而，在大多数情况下，光诱导的相在光关闭后会以超快的时间尺度恢复到平衡状态，从而限制了它们的实际应用。

附：英文原文

Title: Terahertz field-induced metastable magnetization near criticality in FePS₃

Author: Ilyas, Batyr, Luo, Tianchuang, von Hoegen, Alexander, Vias Bostrm, Emil, Zhang, Zhuquan, Park, Jaena, Kim, Junghyun, Park, Je-Geun, Nelson, Keith A., Rubio, Angel, Gedik, Nuh

Issue&Volume: 2024-12-18

Abstract: Controlling the functional properties of quantum materials with light has emerged as a frontier of condensed-matter physics, leading to the discovery of various light-induced phases of matter, such as superconductivity, ferroelectricity, magnetism and charge density waves. However, in most cases, the photoinduced phases return to equilibrium on ultrafast timescales after the light is turned off, limiting their practical applications. Here we use intense terahertz pulses to induce a metastable magnetization with a remarkably long lifetime of more than 2.5 milliseconds in the van der Waals antiferromagnet FePS₃. The metastable state becomes increasingly robust as the temperature approaches the antiferromagnetic transition point, suggesting that critical order parameter fluctuations play an important part in facilitating the extended lifetime. By combining first-principles calculations with classical Monte Carlo and spin dynamics simulations, we find that the displacement of a specific phonon mode modulates the exchange couplings in a manner that favours a ground state with finite magnetization near the Néel temperature. This analysis also clarifies how the critical fluctuations of the dominant antiferromagnetic order can amplify both the magnitude and the lifetime of the new magnetic state. Our discovery demonstrates the efficient manipulation of the magnetic ground state in layered magnets through non-thermal pathways using terahertz light and establishes regions near critical points with enhanced order parameter fluctuations as promising areas to search for metastable hidden quantum states.

DOI: 10.1038/s41586-024-08226-x

Source: https://www.nature.com/articles/s41586-024-08226-x