Collaborative Research: Carrier dispersion and Nontrivial Topological Phases in Ultra-Low Bandgap Metamorphic InAsSb Ordered Alloys

适合发展红外光电子器件的半导体多年来一直受到物理学家和工程师的关注。变质分子束外延是一种用于材料开发的新技术，它可以在广泛的原子浓度范围内精确控制化合物的组成(铟、砷、铝和锑)，从而生产出高质量的化合物。这种能力使人们能够深入研究受材料缺陷保护的重要窄带半导体的“量子”性质。这些特性可能会对包括量子计算机在内的各种设备的性能产生深远的影响。在这个项目中，来自石溪大学和佐治亚理工学院的跨学科研究团队计划使用新材料来实验演示量子物理的有趣特征。这些努力结合了新材料的开发以及通过各种先进的实验技术研究其物理性质和能谱。该项目还为研究生提供物理、材料科学和工程方面的协同培训，为本科生创造研究机会。K-12教育部分的目标是在不损害人类生活质量的情况下，培养使用新材料和技术来提高器件性能的早期意识。该项目是进行高质量纳米有序砷化铟(InAsSb)合金的外延生长，并研究这些材料中新的拓扑非平凡相的表现。材料生长是基于最近发展的虚拟衬底方法，该方法解除了衬底晶格常数的约束。然后，通过改变晶格常数、应变、合金成分和成分调制周期，InAsSb有序合金的物理性能可以控制在一个特殊的程度上。有了这些新材料，研究小组打算回答以下基本问题。(1)在具有纳米有序和带隙可调的变质InAsSb合金中，能否实现和观察到非平凡的拓扑相？(2)InAsSb有序合金能否成为演示Majorana零模的新平台？这些课题具有重大的基础和技术意义，特别是对于拓扑量子计算的固态实现而言。该项目的技术途径包括能带结构计算、先进的外延生长和尖端表征方法。后者具有透射电子显微镜、高分辨率X射线衍射、倒易空间测绘、强磁场红外光谱和角度分辨光电子能谱。参与该项目的研究生和本科生有独特的机会掌握这些方法，并参与材料开发过程的所有阶段。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。

Semiconductors suitable for the development of infrared opto-electronic devices attract attention of physicists and engineers for many years. Metamorphic molecular beam epitaxy, a novel technology for material development, produces high quality compounds with precise control of their composition (indium, arsenic, aluminum and antimony) over a wide range of atomic concentrations. This ability allows deep studies of the "quantum" properties of important narrow-band semiconductors that are protected against material imperfections. These properties may have profound implication for the performance of a variety of devices including quantum computers. In this project the interdisciplinary research team from Stony Brook University and Georgia Institute of Technology plans to use novel materials for experimental demonstration of intriguing features of quantum physics. The efforts combine development of new materials and study of their physical properties and energy spectra by a variety of advanced experimental techniques. The project also provides for synergetic training of graduate students in physics, material science, and engineering, creating research opportunities for undergraduate students. The K-12 education component aims at cultivating an early-stage awareness of using new materials and technologies to improve the device performance without compromising the quality of human life.This project is to carry out epitaxial growth of high-quality indium arsenide antimonide (InAsSb) alloys with controllable nanoscale ordering and to investigate the manifestations of the new topologically nontrivial phases in these materials. The material growth is based on a recently developed virtual substrate approach, which lifts the constraint from the substrate lattice constant. The physical properties of the InAsSb ordered alloys can then be controlled to an exceptional degree, via varying the lattice constant, the strain, the alloy composition, and the composition modulation period. With these new materials, the research team intends to answer the following fundamental questions. (1) Can nontrivial topological phases be realized and observed in metamorphic InAsSb alloys with nanoscale ordering and tunable bandgap? (2) Can the InAsSb ordered alloys be a new platform for demonstration of Majorana zero mode? These topics are of great fundamental and technological interest, particularly for the solid-state realization of topological quantum computing. The technical approaches of the project include band structure calculation, advanced epitaxial growth, and cutting-edge characterization methods. The latter features transmission electron microscopy, high-resolution x-ray diffraction, reciprocal space mapping, infrared spectroscopy in high magnetic fields, and angle-resolved photoemission spectroscopy. Graduate and undergraduate students participating in the project have unique opportunities to master these methods and engage in all stages of the material development process.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.