Topological quantum transport properties in spin-valley locked Dirac semimetals

点击翻译按钮获取中文摘要

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.