Tuning electronic instabilities in triangular surface lattices via subsurface doping

非技术摘要：该项目旨在通过化学掺杂实验来可控地改变单原子薄膜材料的电子性质。所研究的薄膜系统由在硅衬底上以各种三角形图案排列的锡或铊原子组成。单原子TiN层特别令人感兴趣，因为它有可能获得具有可能奇异性质的新型电子材料，例如通过化学掺杂获得超导电性。通过单原子Tl薄膜的化学掺杂可以获得奇特的磁性。原子尺度上对导致这种新兴电子行为的量子力学机制的理解对于推动一类新的电子材料作为可能的硅在信息技术中使用的纳米电子器件中的替代是至关重要的。田纳西大学拟议的科学和辅助基础设施为教育和培训具有国际竞争力的研究生提供了良好的环境。一项将赞助研究与本科教育相结合的严格计划正在实施中，以提高物理专业的招生人数。这项外展计划的目标是参加著名的田纳西州州长科学与工程学校的大二和初中生。通过为所有这些年轻人提供独特的研究和教育经验，研究人员的目标是吸引这些深刻的思想家和未来的决策者攻读物理学的高级学位。技术摘要：提高对复杂材料的认识和实际应用的一个关键方面是通过化学掺杂控制其电子性质的能力。对于一个严格的二维系统，当电离的掺杂杂质成为二维电子系统的组成部分时，化学掺杂不可避免地引入结构无序。该项目建立在早期NSF赞助的研究的主要成果的基础上，在该研究中，表面层或薄膜的空穴掺杂是通过亚表面或调制掺杂实现的。类似于复杂氧化物体系的研究，这些研究的目的是扩大空穴掺杂的浓度范围，并将调制掺杂的概念扩展到n型物种，从而建立全电子相图。这一策略被用于掺杂具有强Mott关联和强自旋-轨道耦合的三角形表面晶格。我们将探讨前者中d波超导电性和后者中自旋密度波不稳定性作为掺杂水平的函数的激发可能性。该项目包括在超高真空中生长薄膜，扫描隧道显微镜和光谱学，以及角度分辨光电子实验，所有这些都与外部合作者的理论支持相结合。田纳西大学拟议的科学和辅助基础设施为教育和培训具有国际竞争力的研究生提供了良好的环境。一项将赞助研究与本科教育相结合的严格计划正在实施中，以提高物理专业的招生人数。这项外展计划的目标是参加著名的田纳西州州长科学与工程学校的大二和初中生。通过为所有这些年轻人提供独特的研究和教育经验，研究人员的目标是吸引这些深刻的思想家和未来的决策者攻读物理学的高级学位。

Non-Technical Abstract:This project aims to controllably modify the electronic properties of monatomic thin film materials via chemical doping experiments. The thin film systems under investigation consist of tin or thallium atoms arranged in various triangular patterns on a silicon substrate. The monatomic tin layer is of particular interest because there is the potential to obtain novel electronic materials with possibly exotic properties, such as superconductivity via chemical doping. Exotic magnetism may be obtained through the chemical doping of monatomic thallium films. Atomic-scale understanding of the quantum mechanical mechanisms that give rise to such emergent electronic behavior is crucial in order to advance a new class of electronic materials as the possible replacement of silicon in, e.g., nano-electronic devices used in information technology. The proposed science and supporting infrastructure at The University of Tennessee provide an excellent setting for the education and training of internationally competitive graduate students. A rigorous plan for integrating sponsored research with undergraduate education is being implemented to boost enrolment in the physics major. The outreach program targets sophomore and junior high school students who are participating in the prestigious Tennessee Governor School for the Sciences and Engineering. By providing all of these young people with unique research and educational experiences, the investigators aim to entice these deep thinkers and future decision-makers to pursue an advanced degree in the physical sciences. Technical Abstract:A critical aspect for advancing knowledge and practical applications of complex materials is the ability to control their electronic properties via chemical doping. For a strictly two-dimensional system, chemical doping inevitably introduces structural disorder as the ionized dopant impurities become an integral part of the two-dimensional electron system. This project builds on the main accomplishments from earlier NSF sponsored research, in which hole doping of a surface layer or thin film was accomplished via subsurface- or ?modulation doping?. In analogy with studies on complex oxide systems, the investigations aim to widen the concentration range of the hole dopants and expand the modulation doping concept to n-type species, so as to establish a full electronic phase diagram. This strategy is being employed to dope triangular surface lattices with strong Mott correlations and strong spin-orbit coupling. The exciting possibilities of d-wave superconductivity in the former, and spin density wave instabilities in the latter will be explored as a function of the doping level. The project involves thin film growth in ultrahigh vacuum, scanning tunneling microscopy and spectroscopy, and angle-resolved photoemission experiments, all in conjunction with theoretical support from outside collaborators. The proposed science and supporting infrastructure at The University of Tennessee provide an excellent setting for the education and training of internationally competitive graduate students. A rigorous plan for integrating sponsored research with undergraduate education is being implemented to boost enrolment in the physics major. The outreach program targets sophomore and junior high school students who are participating in the prestigious Tennessee Governor School for the Sciences and Engineering. By providing all of these young people with unique research and educational experiences, the investigators aim to entice these deep thinkers and future decision-makers to pursue an advanced degree in the physical sciences.