Study of Multiband Effects in MgB2 by Controlling Intraband and Interband Scattering in Epitaxial Films

通过控制外延膜中的带内和带间散射研究MgB2中的多带效应

• 批准号: 0405502
• 负责人: Qi Li
• 金额: --
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-05-01 至 2010-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0405502&HistoricalAwards=false
• 关键词: Study; Multiband; Effects; MgB2; Controlling

The recently discovered superconductivity in magnesium-diboride (MgB2) not only shows the highest superconducting transition temperature of 39 K among the conventional superconductors, but also unique multiband behaviors which distinguish it from conventional BCS superconductors. The interplay between intra- and inter-band coupling and scattering has been proposed to result in many rich and unusual properties. A collaborative group at Penn State has developed a Hybrid Physical-Chemical Vapor Deposition (HPCVD) technique that has produced the cleanest MgB2 thin films reported so far. It also provides a possibility to systematically change intra and interband scattering in the samples. This individual investigator award supports studies of a variety of superconducting and normal state transport properties of MgB2 based thin films with various degrees of coupling and scattering rates. Through collective measurements, the project can ultimately reveal how the presence of two bands changes the superconducting and normal state behaviors in different temperatures, currents, and magnetic fields when the intra and interband scattering rates are systematically varied. This project will have significant impact on understanding the effect of multi-band on physical properties, especially on superconducting properties. It may also lead to an optimized path to large critical field and critical current, which are very significant for potential applications in high field magnet and electric power. The project provides a broad education and training opportunities for graduate students and undergraduate students, especially for undergraduate students from colleges without substantial research infrastructures and high school science teachers through summer research programs. Recently, a new superconductor, magnesium-diboride (MgB2), has been discovered which has the highest superconducting transition temperature (the temperature where the electrical resistance of a material becomes zero) of 39 K among metals. Electrons in a material group themselves into bands. In most conductors and superconductors only the electrons in one band contribute to the conducting and superconducting properties of the material. However, MgB2 has a unique electron band structure in which electrons from multiple bands contribute to these properties. The interplay of electrons scattering within and between bands has been proposed to result in many rich and unusual properties. A collaborative group at Penn State has developed a technique that has produced the cleanest MgB2 thin films reported so far. This technique also provides the possibility of systematically changing the interactions of electrons within and between the bands in the samples. This award supports studies of a variety of superconducting and normal state properties of different MgB2 based thin films. Through various measurements, the project can ultimately reveal how the presence of two bands changes the superconducting and normal state behaviors. The research may also lead to finding an optimized path to obtain materials that remain superconducting in large magnetic fields and capable of carrying a large current, which are very significant for potential applications in high field magnet and electric power. The project provides a broad education and training opportunities for graduate students and undergraduate students, especially for undergraduate students from colleges without substantial research infrastructures and high school science teachers through summer research programs.

最近发现的二硼化镁（MgB_2）超导体不仅具有传统超导体中最高的超导转变温度（39 K），而且具有独特的多带行为，使其区别于传统的BCS超导体。已经提出带内和带间耦合和散射之间的相互作用导致许多丰富和不寻常的属性。宾夕法尼亚州立大学的一个合作小组开发了一种混合物理化学气相沉积（HPCVD）技术，该技术已经产生了迄今为止报道的最干净的MgB2薄膜。它还提供了一种可能性，系统地改变内和带间散射的样品。这个个人研究者奖支持各种超导和正常状态的传输性能的MgB2基薄膜的各种程度的耦合和散射率的研究。通过集体测量，该项目最终可以揭示当带内和带间散射率系统地变化时，两个带的存在如何改变不同温度，电流和磁场中的超导和正常状态行为。该项目将对理解多带效应对物理性质，特别是超导性质的影响产生重大影响。它还可以导致一个优化的路径，以大的临界磁场和临界电流，这是非常重要的潜在应用在高场磁体和电力。该项目通过暑期研究项目为研究生和本科生提供了广泛的教育和培训机会，特别是为来自没有实质性研究基础设施的大学的本科生和高中科学教师提供了机会。最近，已经发现了一种新的超导体，二硼化镁（MgB 2），其在金属中具有39K的最高超导转变温度（材料的电阻变为零的温度）。物质中的电子组成电子带。 在大多数导体和超导体中，只有一个能带中的电子对材料的导电性和超导性有贡献。然而，MgB2具有独特的电子能带结构，其中来自多个能带的电子有助于这些性质。电子在能带内和能带间的相互作用导致了许多丰富而不寻常的性质。宾夕法尼亚州立大学的一个合作小组开发了一种技术，可以生产出迄今为止报道的最干净的MgB2薄膜。该技术还提供了系统地改变样品中带内和带间电子相互作用的可能性。该奖项支持不同MgB2基薄膜的各种超导和正常状态特性的研究。通过各种测量，该项目最终可以揭示两个能带的存在如何改变超导和正常状态行为。该研究还可能导致找到一种优化的路径，以获得在大磁场中保持超导并且能够承载大电流的材料，这对于高场磁体和电力的潜在应用非常重要。该项目通过暑期研究项目为研究生和本科生提供了广泛的教育和培训机会，特别是为来自没有实质性研究基础设施的大学的本科生和高中科学教师提供了机会。