CAREER: Multiferroicity in van der Waals Heterostructures

非技术性描述：铁磁和铁电材料可用于构建新型量子器件，即使在没有外场的情况下也可利用其磁性。当铁磁和铁电材料集成在一起，形成所谓的“多铁性”时，材料功能大大增强，超出了两种材料的简单组合，导致新的磁电现象。特别是当这些材料是原子级薄时，它们的相互作用变得更加奇特。新兴的铁磁和铁电材料提供了有趣的积木逐层组装的新型多铁性异质结构。理解这种异质结构中多铁性的基本磁电物理，从而开发有效的方法来操纵多铁性，对于推进这些新兴的异质结构用于超紧凑，节能的自旋电子器件具有基础性意义。该项目研究了静电掺杂，电场，界面化学和晶格应变对所得多铁性的影响，可能导致工程方法的发展，以推进人类对新型功能异质结构的控制。不同层次的学生，包括研究生，本科生和高中生，来自各种背景，在2D异质结构组装，纳米器件制造，低温硬件制造和操作，以及各种显微镜和光谱学的广泛专业知识进行培训。该项目有助于加强美国未来量子信息科学和技术的劳动力，并通过开发新的课程材料和地方和区域教育活动来提高公众对量子技术的认识。技术描述：最近出现的铁磁和铁电2D vdW材料是具有长程铁电有序的原子级薄晶体，为探索低维自旋和偶极物理提供了理想的凝聚态平台。当2D铁磁体和2D铁电体被集成以形成多铁性异质结构时，不同铁性有序之间的相互作用可以产生过多的涌现磁电现象，可能导致新颖的低功率自旋电子器件。本计画的研究目的是探讨vdW异质结构中磁电多铁性的基本机制，包括电荷转移诱导掺杂、内建电场、界面杂化及压电应变效应。鉴于这些因素在异质结构系统中无处不在，理解它们在所得多铁性中的作用可以为设计功能性vdW异质结构提供关键见解，这可能会改变铁性量子异质结构的景观，并实现破坏性自旋电子和量子技术。基于这些基本的理解，可以开发有效的工程方法来创建具有理想的磁电物理特性的异质结构。主要的研究方法包括组装各种类型的vdW多铁性异质结构和制造基于这些异质结构的器件，并通过静电掺杂，电场和压电应变进一步工程化。通过一系列显微镜和光谱仪探测所产生的物理特性。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。

Nontechnical description: Ferromagnetic and ferroelectric materials can be used to build novel quantum devices, utilizing their magnetic properties even in absence of external fields. When ferromagnetic and ferroelectric materials are integrated together, forming the so-called “multiferroics”, the material functions are largely enhanced beyond the simple combination of two materials, leading to novel magnetoelectric phenomena. Especially when these materials are atomically thin, their interactions become even more exotic. The emerging ferromagnetic and ferroelectric materials provide intriguing building blocks for layer-by-layer assembling of novel multiferroic heterostructures. Understanding the fundamental magnetoelectric physics underlying the multiferroicity in such heterostructures and thereby developing effective approaches to manipulate the multiferroicity, have foundational significance for advancing these emerging heterostructures for ultracompact, energy-efficient spintronic devices. This project studies the effects of electrostatic doping, electric field, interfacial chemistry, and lattice strain on the resultant multiferroicity, potentially leading to the development of engineering approaches to advance human control of the new class of functional heterostructures. Students of various levels, including graduate, undergraduate, and high-school students, from all backgrounds, are trained with a broad range of expertise in 2D heterostructure assembling, nanodevice fabrication, cryogenic hardware manufacturing and operation, and a variety of microscopies and spectroscopies. This project can help strengthen the future workforce for the quantum information science and technologies in the U.S. and raise the public literacy of quantum technologies by the development of new course materials and local and regional educational activities.Technical description: The recently emerged ferromagnetic and ferroelectric 2D vdW materials are atomically thin crystals with long-range ferroic orders, providing ideal condense matter platforms for exploring the low-dimensional spin and dipole physics. When 2D ferromagnets and 2D ferroelectrics are integrated to form multiferroic heterostructures, the interplay between the disparate ferroic orders can generate a plethora of emergent magnetoelectric phenomena, potentially leading to novel low-power spintronic devices. The research objective of this project is to elucidate the fundamental mechanisms underlying the magnetoelectric multiferroicity in vdW heterostructures, including charge transfer induced doping, built-in electric field, interfacial hybridization, and piezoelectric strain effect. Given these factors are ubiquitous in heterostructure systems, understanding their roles in the resultant multiferroicity can provide critical insights for designing functional vdW heterostructures, which potentially transforms the landscape of ferroic quantum heterostructures and enabling disruptive spintronic and quantum technologies. Based on these fundamental understandings, effective engineering approaches can be developed to create heterostructures with desirable magnetoelectric physical properties. The main research approaches include assembling various types of vdW multiferroic heterostructures and fabricating these heterostructures based devices, which are further engineered by electrostatic doping, electric field, and piezoelectric strain. The resultant physical properties are probed by a range of microscopies and spectroscopiesThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.