EFRI 2-DARE: Engineering novel topological interface states in 2D chalcogenide heterostructures

太赫兹传感和成像是一个？大挑战?这会影响医疗成像和国家安全。在过去的几十年里，太赫兹/红外探测的材料和器件制造取得了巨大的进步。然而，传统技术只允许在设备中使用一个有源元件检测单个波长，严重阻碍了太赫兹/红外传感器的小型化和功能性。这个EFRI团队将利用拓扑绝缘体，这是凝聚态物理学的最新突破。该团队的目标是设计驻留在拓扑绝缘体和传统半导体之间边界的拓扑界面状态。由于拓扑绝缘体的拓扑非平凡电子结构，这种界面态具有抗缺陷的鲁棒性。此外，拓扑界面态在动量空间中具有丰富的自旋织构，这为其杂化与电压（门控）和磁场的调节提供了可能。该团队将解决材料合成、光电和自旋电子器件的实现及其表征方面的挑战。该项目设想的设备概念是潜在的改变游戏规则的技术，直接解决太赫兹/红外技术领域的巨大挑战和国家需求。学生的教育和培训与研究活动无缝结合，使他们能够学习基础材料科学，掌握先进的微观技术，更重要的是学会独立思考。该项目还通过罗格斯大学（Rutgers）、RPI和约翰霍普金斯大学（John Hopkins）的各种项目，对代表性不足的本科生进行教育和培训，并通过自由科学中心（Liberty Science Center）的科学合作伙伴项目，对高中生进行教育和培训。拓扑绝缘体是一种新型的物质量子态，在其体带隙内具有螺旋狄拉克表面态。与传统异质结构界面上的二维电子气体（2DEG）相比，这些强大的拓扑表面态由于其自旋动量锁定而不受后向散射的影响。本项目的目标是通过设计拓扑绝缘体与半导体界面的拓扑状态来探索新的器件应用。初步的理论工作表明，这些拓扑界面态可以与自由表面的表面态有质的不同，因为它们具有完全不同的自旋动量锁定结构。在先进的第一性原理理论和模型（Zhang+West）的指导下，将用最先进的MBE （Oh）合成高质量的薄膜和拓扑绝缘体的异质结构，并使用输运（Oh）、扫描隧道显微镜和光谱（Wu）和太赫兹和光学光谱（Armitage）进行表征。理论，合成和表征之间的密切反馈承诺新的器件物理和应用。提出的工作的具体目标包括两个特定的器件，一个可调谐太赫兹范围光子探测器和一个全极化自旋极化电流源。这些都是改变游戏规则的技术。尽管针对这类材料提出了许多可能的装置，但到目前为止，实际实现的很少。随着这些pi及其专业领域的最新进展，在拓扑绝缘体的这些应用中协同推动的时机已经成熟。

Terahertz sensing and imaging is a ?grand challenge? that impacts medical imaging and national security. Tremendous progress has been made on materials and device fabrication of terahertz/infrared detection in the past decades. However, the conventional technologies only allow detection of single wave lengths with one active element in device, severely hampering the miniature and functionality of terahertz/infrared sensors. This EFRI team will harness topological insulator, a recent breakthrough in condensed matter physics. The team aims to engineer topological interface states residing at the boundary between a topological insulator and a conventional semiconductor. Such interface states are robust against imperfection due to topologically non-trivial electronic structure of topological insulator. Furthermore, topological interface states host rich spin-texture in momentum space, which opens the possibility of tuning their hybridization with electrical voltage (gating) and magnetic field. The team will address the challenges of materials synthesis, realization of optoelectronic and spintronic devices, and their characterizations. The device concepts envisioned in this project are potentially game-changing technologies, directly addressing the grand challenge and national need on the terahertz/infrared technological areas. Education and training of students is seamlessly integrated to the research activities, which enable them to learn fundamental material science, to master advanced microscopic techniques, and more importantly, to learn independent thinking. This project also integrates education and training of under-represented undergraduate students through various programs at Rutgers, RPI and John Hopkins, and of high school students through the Partner in Science program of Liberty Science Center. Topological insulators are novel quantum states of matter, which host helical Dirac surface states within their bulk band gap. These robust topological surface states are immune to backscattering because of their spin-momentum locking, in contrast to the conventional 2-dimensional electron gases (2DEG) that reside at interfaces in conventional heterostructures. The objective of this project is to explore novel device applications by engineering the topological states at the interfaces of topological insulators with semiconductors. Preliminary theoretical work shows that these topological interface states can be qualitatively different from the surface states of the free surfaces in that they have completely different textures of spin-momentum locking. With the guidance of advanced first principle theory and modeling (Zhang+West), high quality thin films and heterostructures of topological insulators will be synthesized with state-of-the-art MBE (Oh), and characterized with transport (Oh), scanning tunneling microscopy and spectroscopy (Wu) and THz and optical spectroscopy (Armitage). The intimate feedback between theory, synthesis and characterization promises novel device physics and applications. The specific goals of the proposed work include two specific devices in the form of a tunable THz range photon detector and a source of fully polarized spin polarized current. These are both game changing technologies. Although many possible devices have been proposed for this class of materials, little has been actually realized thus far. With recent advances by these PIs and their areas of expertise, the time is ripe for a concerted push in these applications of topological insulators.