Physics of Proximate Metallic and Insulating Phases

****非技术摘要****该项目将进行实验，以制造和表征金属和绝缘体接近的材料。在给定的材料中，金属相和绝缘相的接近以两种方式出现：两相同时共存并相互竞争，或者一个主导相可以转变为另一个。在这两种情况下，外部参数（如温度或磁场）的变化都会引起金属-绝缘体的转变，并伴随着电性能的显著变化。所选择的研究材料包括超薄无序铁磁薄膜（可通过金属-绝缘体过渡调谐）、复合氧化物（由铁磁金属相和绝缘相竞争组成）、掺杂石墨（与碳平面平行/垂直）和“拓扑绝缘体”（由于其不同寻常的电子结构，导电边缘和表面状态与绝缘内部共存）。了解这些研究的结果有望揭示重要的新物理学，这将推动新型复合金属-绝缘体材料的设计，这可能对社会的新技术很重要。该提案支持的研究和教育/推广活动将导致研究生和本科生在学术，工业或政府环境中获得满意和富有成效的职业生涯。****技术摘要****该项目将进行实验，以制造和表征金属相和绝缘相非常接近的材料，从而产生复杂而新颖的现象。所选择的研究材料主要有四类：(1)超薄铁磁薄膜，可以通过改变无序强度通过金属-绝缘体转变进行调谐；(2)在绝缘体-金属渗透过渡附近共存的金属相和绝缘相之间存在温度、应变和场相关竞争的混合相锰矿；(3)石墨中嵌层诱导的面内“超金属”导电性与面外绝缘导电性同时存在；(4)拓扑绝缘体，由于其独特的电子带结构，导电边缘和表面状态与绝缘内部共存。了解这些研究的结果有望揭示重要的新物理学，这将推动在近似金属和绝缘阶段统一主题下，在纳米尺度上设计新型复合金属-绝缘体材料。这项研究的相关研究和教育/推广活动将导致研究生和本科生在学术，工业或政府环境中获得满意和富有成效的职业生涯。

**** NON-TECHNICAL ABSTRACT ****This project will pursue experiments to fabricate and characterize materials in which metals and insulators are in close proximity. The proximity of metallic and insulating phases in a given material arises in two ways: both phases simultaneously coexist and compete with each other, or one dominant phase can be transformed to the other. In both cases the change of an external parameter such as temperature or magnetic field can induce metal-insulator transitions accompanied by pronounced changes in electrical properties. The materials chosen for study include ultra thin disordered ferromagnetic films which can be tuned through a metal-insulator transition, complex oxides which comprise competing ferromagnetic metal and insulating phases, doped graphite which exhibits highly metallic/insulating behavior parallel/perpendicular to the carbon planes, and "topological insulators", which by virtue of their unusual electronic structure have conducting edge and surface states coexisting with insulating interiors. Understanding the results of these studies promises to unveil important new physics that will drive the design of novel composite metal-insulator materials that may be important for new technologies for the benefit of society. The research and education/outreach activities supported by this proposal will lead to the placement of graduate and undergraduate students in satisfying and productive professional careers within academic, industrial or government settings.**** TECHNICAL ABSTRACT ****This project will pursue experiments to fabricate and characterize materials in which metallic and insulating phases are in close proximity, thereby giving rise to complex and novel phenomenology. The materials chosen for study focus on four classes: (1) ultra thin ferromagnetic films that can be tuned through a metal-insulator transition by varying the disorder strength; (2) mixed phase manganites in which there is a temperature, strain and field-dependent competition between coexisting metallic and insulating phases near an insulator-metal percolation transition; (3) graphite in which there is an intercalation-induced in-plane "supermetallic" conductivity simultaneously appearing with an out-of-plane insulating conductivity; and (4) topological insulators, which by virtue of their unusual electronic band structure have conducting edge and surface states coexisting with insulating interiors. Understanding the results of these studies promises to unveil important new physics that will drive the design of novel composite metal-insulator materials at nanoscale dimensions under the unifying theme of proximate metallic and insulating phases. The associated research and education/outreach activities of this research will lead to the placement of graduate and undergraduate students in satisfying and productive professional careers within academic, industrial or government settings.