Van-der-Waals magnets: Frustrated magnetism, magnetotransport, and optically driven excitations

范德华磁体：受抑磁性、磁输运和光驱动激励

• 批准号: 449890867
• 负责人: Dr. Urban Seifert
• 金额: --
• 依托单位: Kavli Institute for Theoretical Physics
• 依托单位国家: 德国
• 项目类别: WBP Fellowship
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/449890867?language=en
• 关键词: Van; der; Waals; magnets; Frustrated

Condensed matter systems in low dimensions often show behavior and exotic phenomena markedly different from their three-dimensional bulk analogues. A particularly fruitful platform to study these effects and design systems with desired characteristics are two-dimensional few-layer heterostructures based on exfoliated van-der-Waals materials. These novel devices allow for an unprecedented degree of control of strongly correlated electrons by e.g. varying the relative displacement between layer (including twisting) or electric gating. Only in 2017, first evidence for magnetism in mono- and few-layer van-der-Waals (vdW) systems was found. Since then, remarkable experimental progress has uncovered several other vdW materials exhibiting various ferro- and antiferromagnetic ordering patterns. Many of these systems feature strongly enhanced magnetooptical effects, novel tunneling magnetoresistance and magnetoelectric effects, and strong coupling between magnetic and lattice degrees of freedom.This project has the goal of gaining a thorough understanding of novel phenomena in few-layer van-der-Waals systems, with the aim of both identifying novel phenomena and proposing experimental protocols, as well as theoretically modelling previously observed effects.To this end, in the first part of this project, we employ a continuum model to study the impact of strong spin-lattice coupling on the non-collinear ground states and excitations in the recently proposed frustrated Moiré magnets obtained by twisting a bilayer magnet.Second, we will investigate novel phases induced by a magnetic field in these twisted bilayer magnets and compute the corresponding spin-wave dispersions by modelling interlayer magnon tunneling for arbitrary lattice displacements.The third part of this project is concerned with the novel magnetism-dependent interlayer electronic transport observed in some semiconducting magnetic van-der-Waals few-layer systems, in particular CrI3. Here, we plan to model low-energy electronic excitations in an effective mass model and then couple this model to a continuum theory for magnetism in the few-layer systems.Lastly, we will explore to what extent ultrafast optical methods can be used to excite magnetic excitations in magnetic vdW systems, in particular also utilizing spin-lattice coupling, and study non-equilibrium dynamics in these heterostructures.

低维凝聚态系统通常表现出与三维大块类似物明显不同的行为和奇异现象。一个特别富有成效的平台，研究这些影响和设计系统所需的特性是二维的几层异质结构的剥离范德华材料的基础上。这些新颖的器件允许通过例如改变层之间的相对位移（包括扭曲）或电门控来对强关联电子进行前所未有的控制。仅在2017年，才首次发现单层和少层范德华（vdW）系统的磁性证据。此后，显着的实验进展发现了其他几种表现出各种铁磁和反铁磁有序模式的vdW材料。其中许多系统具有强烈增强的磁光效应、新颖的隧穿磁电阻和磁电效应以及磁自由度和晶格自由度之间的强耦合。本项目的目标是深入了解少层范德华系统中的新现象，目的是识别新现象并提出实验方案，以及从理论上模拟先前观察到的影响。为此，在本项目的第一部分，我们采用连续介质模型来研究强自旋-晶格耦合对非-最近提出的通过扭转双层磁体获得的受抑莫尔磁体中的共线基态和激发。第二，我们将研究这些扭曲双层磁体中由磁场引起的新相位，并计算相应的自旋，波色散的模拟层间磁振子隧穿任意晶格位移。本项目的第三部分是关于新的在一些半导体磁性范德华少层系统中观察到的与磁性相关的层间电子输运，特别是CrI 3。在这里，我们计划在一个有效质量模型中模拟低能量电子激发，然后将此模型耦合到一个连续理论的磁性在几层system. Finally，我们将探讨在何种程度上超快光学方法可以用来激发磁vdW系统中的磁激发，特别是还利用自旋晶格耦合，并研究这些异质结构的非平衡动力学。