Correlated Electron Effects in Small Clusters in Low Temperatures Molecular Beams

低温分子束中小团簇中的相关电子效应

• 批准号: 0605894
• 负责人: Walter De Heer
• 金额: $ 36万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0605894&HistoricalAwards=false
• 关键词: Correlated; Electron; Effects; Small; Clusters

*****NON-TECHNICAL ABSTRACT**** Metal clusters, composed of a few to a few hundred atoms, are prototypical nanoscale objects. Their intrinsic properties are studied in molecular beams in a vacuum where they are not affected by supporting structures. Many interesting properties result when the motion of the conduction electrons in metals becomes correlated. The best known of these are ferromagnetism and superconductivity. This project will use molecular beam studies to trace the evolution of these properties as a function of cluster size. For example, the magnetic properties of an iron cluster composed of 5 atoms are different than those of a cluster with 500 atoms, and both exhibit recognizable bulk magnetic features. Insight into these evolutionary trends in magnetism will help in designing novel nano-magnetic materials, which are important for the recording industry. The students participating in this research will learn scientific concepts and state-of-the-art techniques, which will prepare them for careers in academic, industrial, or governmental research. In addition, outreach to high school science teachers is planned. This project is supported by the Condensed Matter Physics program in the Division of Materials Research and the Atomic, Molecular, and Optical Physics program in the Physics Division.*****TECHNICAL ABSTRACT**** This individual investigator award supports a project using state of the art low-temperature molecular beam methods developed at GIT to measure properties of a wide variety of metal clusters as a function of mass and temperature (T=10-300 K). Support-free clusters at very low temperatures are particularly important, not only because their properties can be accurately measured with precise knowledge of their size, but also because a relatively large fraction of the clusters in the beam are frozen in their quantum mechanical ground states. This virtually unexplored state of matter provides a unique opportunity to investigate electronic properties and electronic phase transitions involving ferromagnetism, ferroelectricity and superconductivity. The relationship of the ferroelectric phase transition to superconductivity in Nb, V, and Ta, clusters will be examined. In addition cluster ferromagnetism will be investigated. In particular for cobalt clusters a ground state with 2 Bohr magnetons per atom and an electronically excited state with about 1 Bohr magneton per atom has been observed. This observation suggests a mechanism for the evolution of molecular magnetism to bulk itinerant ferromagnetism. The students involved with this research will learn scientific concepts and state-of-the-art techniques, which will prepare them for careers in academic, industrial, or governmental research. In addition, outreach to high school science teachers is planned. This project is supported by the Condensed Matter Physics program in the Division of Materials Research and the Atomic, Molecular, and Optical Physics program in the Physics Division

*非技术抽象*金属团簇，由几个到几百个原子组成，是典型的纳米级物体。它们的本征性质是在真空中的分子束中研究的，在那里它们不受支撑结构的影响。当传导电子在金属中的运动变得相关时，就会产生许多有趣的性质。其中最著名的是铁磁性和超导电性。这个项目将使用分子束研究来追踪这些性质作为星团大小的函数的演变。例如，由5个原子组成的铁团簇的磁性与由500个原子组成的铁团簇的磁性不同，并且两者都表现出可识别的体磁特征。洞察磁性的这些演变趋势将有助于设计新的纳米磁性材料，这对唱片行业非常重要。参与这项研究的学生将学习科学概念和最先进的技术，这将为他们在学术、工业或政府研究领域的职业生涯做好准备。此外，还计划与高中理科教师进行接触。这个项目得到了材料研究部的凝聚态物理项目和物理部的原子、分子和光学物理项目的支持。*技术摘要*这个个人研究人员奖支持一个项目，该项目使用GIT开发的最先进的低温分子束方法来测量各种金属团簇的性质作为质量和温度的函数(T=10-300K)。在极低温度下的无支撑星团尤为重要，这不仅是因为可以通过精确地了解它们的大小来精确测量它们的性质，还因为光束中相对较大比例的星团冻结在它们的量子力学基态中。这种几乎未被探索的物质状态为研究涉及铁磁性、铁电性和超导电性的电子性质和电子相变提供了一个独特的机会。我们将研究Nb、V和Ta团簇中铁电相变与超导电性的关系。此外，还将研究团簇的铁磁性。特别是，对于钴原子团簇，观察到了每个原子有2个玻尔磁子的基态和每个原子有大约1个玻尔磁子的电子激发态。这一观察结果表明了分子磁性向块体巡回铁磁性演化的一种机制。参与这项研究的学生将学习科学概念和最先进的技术，这将为他们在学术、工业或政府研究领域的职业生涯做好准备。此外，还计划与高中理科教师进行接触。该项目得到了材料研究部的凝聚态物理计划和物理部的原子、分子和光学物理计划的支持