CAREER: Emergent quantum phenomena in epitaxial thin films of topological Dirac semimetal and its heterostructures

职业：拓扑狄拉克半金属及其异质结构外延薄膜中的量子现象

• 批准号: 2339309
• 负责人: JYOTI KATOCH
• 金额: $ 68.15万
• 依托单位: Carnegie-Mellon University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-06-01 至 2029-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2339309&HistoricalAwards=false
• 关键词: CAREER; Emergent; quantum; phenomena; epitaxial

Nontechnical description:Topological phases of matter have attracted great attention in condensed matter physics due to their rich physics and possible revolutionary technological applications. Three-dimensional topological Dirac semimetals are of great interest due to their intriguing electronic band structure and are an ideal platform to realize emergent quantum phases, dissipationless transmission of electrons, efficient generation of spin current for spintronics, and advanced quantum device concepts such as the topological field effect transistor. The goal of this research project is to explore emergent topological phenomena in a three-dimensional topological Dirac semimetal as tuned by film thickness, external electric field, and magnetic interactions. The principal investigator and research team plans to synthesize high quality epitaxial thin films of a topological Dirac semimetal candidate, Na3Bi, and its heterostructures with magnetic insulators using molecular beam epitaxy. Employing in-operando nano-focused angle-resolved photoemission spectroscopy, the research team plans to directly probe, with no assumptions, the complex electronic band structure that is ultimately responsible for novel phenomena in this class of quantum materials. This project plans to support the doctorate dissertation of a graduate student, through training on different experimental techniques, critical thinking and solving complex research problems. The principal investigator also plans to provide research experience for undergraduate students in her lab every summer, for multiple years from a minority serving institution. The recruitment of the undergraduate students is facilitated through the existing tie-ups with the minority serving institutions. By taking advantage of this research program, the principal investigator proposes to design and implement a new advanced lab course to provide hands-on lab experience to students on research-grade equipment. Also, the plans to develop educational initiatives for a diverse population including an outreach program targeted towards middle and high school students belonging to underrepresented minorities in southwestern Pennsylvania. Technical description:The principal investigator proposes a comprehensive research project to study emergent quantum phenomena in epitaxial thin films of a topological Dirac semimetal and its heterostructures. This research is enabled by a unique home-built ultrahigh vacuum cluster system comprising of experimental capabilities of molecular beam epitaxy, in-situ thin film patterning, and in-situ cryogenic magnetotransport, which allows the research team to synthesize and measure thin films of a topological Dirac semimetal in pristine conditions. The research team plans to utilize molecular beam epitaxy to obtain high quality epitaxial thin films of Na3Bi and its heterostructures with magnetic insulators. The research team plans to employ quantum transport measurements to study thickness dependent non-trivial to trivial band gap insulator transitions, electric field controlled topological phases, and T-broken topological states in thin films of Na3Bi with integrated top and bottom electrostatic gates. In addition, the research team plans to utilize a state-of-the-art nano-focused in-operando angle-resolved photoemission spectroscopy with sub-100 nm spatial resolution to measure the Fermi level dependent (using integrated electrostatic back gate) topological band structure of Na3Bi thin films and their devices.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.

非技术描述：物质的拓扑相因其丰富的物理性质和可能的革命性技术应用而在凝聚态物理领域引起了极大的关注。三维拓扑狄拉克半金属因其有趣的电子能带结构而引起人们极大的兴趣，并且是实现涌现量子相、电子无耗散传输、自旋电子学自旋电流的有效生成以及拓扑等先进量子器件概念的理想平台。场效应晶体管。该研究项目的目标是探索三维拓扑狄拉克半金属中由膜厚度、外部电场和磁相互作用调节的新兴拓扑现象。首席研究员和研究团队计划利用分子束外延合成拓扑狄拉克半金属候选物Na3Bi及其异质结构的高质量外延薄膜和磁绝缘体。研究小组计划采用操作中纳米聚焦角分辨光电子能谱，在没有任何假设的情况下直接探测复杂的电子能带结构，该结构最终导致此类量子材料中的新现象。该项目计划通过不同实验技术、批判性思维和解决复杂研究问题的培训来支持研究生的博士学位论文。首席研究员还计划每年夏天在她的实验室为本科生提供来自少数族裔服务机构的多年研究经验。通过与少数族裔服务机构的现有合作，促进了本科生的招生。通过利用该研究计划，首席研究员建议设计和实施一门新的高级实验室课程，为学生提供研究级设备的实践实验室经验。此外，该计划还计划为多元化人群制定教育计划，包括针对宾夕法尼亚州西南部代表性不足的少数族裔的中学生和高中生的外展计划。 技术描述：首席研究员提出了一个综合研究项目，研究拓扑狄拉克半金属及其异质结构的外延薄膜中的涌现量子现象。这项研究是通过独特的自制超高真空团簇系统实现的，该系统包括分子束外延、原位薄膜图案化和原位低温磁输运的实验能力，该系统使研究团队能够合成和测量薄膜原始条件下的拓扑狄拉克半金属。研究小组计划利用分子束外延技术获得高质量的Na3Bi外延薄膜及其具有磁绝缘体的异质结构。研究小组计划利用量子输运测量来研究具有集成顶部和底部静电门的 Na3Bi 薄膜中与厚度相关的非平凡到平凡的带隙绝缘体转变、电场控制的拓扑相和 T 破碎拓扑态。此外，研究团队计划利用空间分辨率低于100 nm的最先进的纳米聚焦操作内角分辨光电子能谱来测量费米能级相关（使用集成静电背栅）拓扑带Na3Bi 薄膜及其器件的结构。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。