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维持国家在新兴量子技术中的领导地位至关重要。其中一些新的特性包括“非线性霍尔效应”和“谷霍尔效应”，这些特性在量子器件和下一代无线网络等应用中具有吸引力。该项目涉及生产这些材料并研究这些特性以及它们在室温下发挥作用的能力。该项目为培训学生和培养他们成为未来高科技行业的劳动力提供了丰富的机会。本科生，包括那些来自代表性不足的少数群体，将被招募和培训，以增长的材料和执行测量，以发现他们的属性。当地高中学生也将通过参加“让它重要营”外联活动参与进来。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形式的信息载体。当谷自由度与破缺的反转对称性和强的自旋轨道耦合相结合时，它可以产生以自旋谷锁定为特征的独特电子态，从而产生奇异的量子输运现象，如谷和非线性霍尔效应。这些新概念为谷电子和太赫兹探测器等新器件应用奠定了基础。本项目旨在演示自旋谷锁定狄拉克半金属BaMnSb 2和其他几种材料的室温体非线性霍尔和谷霍尔效应。该项目的主要研究人员通过大块单晶生长，微尺度霍尔器件制造，非线性传输测量和光学成像来实现这些目标。谷霍尔效应仅在二维材料中观察到，但从未在任何体材料中报道过。虽然非线性霍尔效应以前在几种2D/3D材料中得到了证实，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。该研究项目将为教学，培训和学习提供丰富的机会。几名本科生，包括代表性不足的少数民族学生，在每个项目年度接受培训，以种植该项目中使用的单晶并进行传输测量。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值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.