Topological quantum transport properties in spin-valley locked Dirac semimetals

非技术描述：开发具有新特性的材料对于保持国家在新兴量子技术方面的领导地位至关重要。其中一些新颖的性质包括“非线性霍尔效应”和“山谷霍尔效应”，它们对量子器件和下一代无线网络等应用具有很大的吸引力。该项目包括生产这些材料，并研究这些性能以及它们在室温下发挥作用的能力。该项目为培养学生和为未来高科技行业的劳动力做准备提供了丰富的机会。本科生，包括那些来自代表不足的少数群体的学生，将被招募并接受培训，以种植材料并进行测量，以发现它们的特性。当地的高中生也将通过参加“让它变得重要”的外展活动而参与进来。技术描述：材料电子结构中的谷自由度已被提出作为一种新的信息载体形式。当山谷自由度与破缺的反转对称性和强烈的自旋-轨道耦合结合在一起时，它可以创建以自旋-山谷锁定为特征的独特电子态，从而产生山谷和非线性霍尔效应等奇异的量子输运现象。这些新概念为电子电子和太赫兹探测器等新设备的应用奠定了基础。本项目旨在演示自旋谷锁定的Dirac半金属BaMnSb2和其他几种材料的室温体非线性霍尔效应和谷霍尔效应。该项目的主要研究人员通过块状单晶生长、微尺度霍尔器件制作、非线性输运测量和光学成像来追求这些目标。谷霍尔效应只在二维材料中被观察到，但从未在任何散体材料中被报道。尽管非线性霍尔效应以前在几种2D/3D材料中表现出来，但它主要是一种低温现象。室温体非线性霍尔效应尚未实现。这一研究项目将为教学、培训和学习创造丰富的机会。几名本科生，包括少数族裔学生，接受了生长单晶的培训，并在每个项目年进行运输测量。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL DESCRIPTION: Developing materials with novel properties is essential for sustaining the nation’s leadership in emerging quantum technologies. Some of those novel properties include “nonlinear Hall effect” and “valley Hall effect” which are attractive for applications such as quantum devices and next-generation wireless networks. This project involves producing these materials and investigating these properties as well as their ability to function at room temperature. The project provides rich opportunities for training students and preparing them as future workforce in high-tech industries. Undergraduate students, including those from the underrepresented minority groups, will be recruited and trained to grow the materials and perform measurements to discover their properties. Local high school students will also be engaged through their participation in the “Make it Matter Camp” outreach. TECHNICAL DESCRIPTION: The valley degree of freedom in the electronic structure of a material has been proposed as a new form of information carrier. When the valley degree of freedom is combined with broken inversion symmetry and strong spin-orbital coupling, it can create a unique electronic state characterized by spin-valley locking, resulting in exotic quantum transport phenomena such as the valley and nonlinear Hall effects. These new concepts lay a foundation for new device applications such as valleytronics and terahertz detectors. This project aims to demonstrate room-temperature bulk nonlinear-Hall and valley-Hall effects in spin-valley-locked Dirac semimetal BaMnSb2 and several other materials. The principal investigator of this project pursues these goals through bulk single crystal growth, microscale Hall device fabrications, nonlinear transport measurements, and optical imaging. The valley Hall effect was observed only in two-dimensional materials but never reported for any bulk materials. Although the nonlinear Hall effect was previously demonstrated in several 2D/3D materials, it is a primarily low-temperature phenomenon. The room-temperature bulk nonlinear Hall effect is yet to be realized. This research project will generate rich opportunities for teaching, training, and learning. Several undergraduate students, including underrepresented minority students, are trained to grow the single crystals used in this project and perform transport measurements in each project year.This 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.