Tuning electronic instabilities in triangular surface lattices via subsurface doping

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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.