Superconductivity and Proximity Effect in Two-Dimensional Films and Multilayers

二维薄膜和多层膜中的超导性和邻近效应

• 批准号: 0803958
• 负责人: Aharon Kapitulnik
• 金额: $ 44万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-01 至 2011-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0803958&HistoricalAwards=false
• 关键词: Superconductivity; Proximity; Effect; Two; Dimensional

Non-Technical AbstractQuantum phase transitions continue to attract intense theoretical and experimental interest. Such transitions -- where changing an external parameter in the Hamiltonian induces a transition from one quantum ground state to another, fundamentally different one -- have been invoked to understand experimental data in many electronic systems, as well as to analyze more challenging quantum phenomena such as the limitations of quantum computing. A paradigm for quantum phase transitions has been the superconductor to insulator transition in two-dimensional films. This transition is found to have a variety of realizations depending on intrinsic properties of the materials used. Controlling the strength of superconductivity, disorder, or dimensionality of the films will impact the nature of the transition, which is accessed through the variation of external parameters such as temperature and magnetic field. This award supports a project to explore the superconductor to insulator transition in amorphous MgB2 films and multilayers. The uniqueness of this system is the ability to control the strength of superconductivity over a very wide range, control the disorder, and fabricate bilayers and multilayers. However, more uniquely, due to the lightness of both magnesium and boron, spin orbit interaction is probably the lowest that can be achieved in any thin film superconductor, providing us with new opportunities to study its effect on the transition. The proposed work is expected to impact science in several areas including shedding new light on the nature of quantum phase transitions in reduced dimensions, better understanding of the material science of amorphous superconducting films, and the development of new methodologies using novel measurements techniques. The program involves graduate students in this area of great interest to physics and future applications.Technical AbstractStudies of the phase diagram of two-dimensional superconductors has been intimately connected to finding new materials. With each materials system a different set of properties is highlighted. Over the years, NSF support enabled the optimization of a variety of materials for studies of thin superconducting films in general and the superconductor to insulator transition (SIT) in particular. These include amorphous-MoGe films that allowed the discovery of "metallic phases," amorphous-InOx films that allowed the studies of the regime of strong disorder, and more recently amorphous- MgB2 films which in addition to the overlap in parameters with MoGe and InOx, also provide a new knob in the form of controlling spin-orbit interaction. A newly available, novel technique to fabricate multilayers of amorphous MgB2/MgO allows further exploration of dimensionality effects. This award supports a project to explore the rich physics this MgB2 model system offers. Experiments will be performed to study SIT in perpendicular magnetic field on MgB2 thin films bilayers of various types (e.g. proximity systems) and multilayers. Specific attention will be given to the effect of quantum melting near the SIT point. The manifestation of low spin-orbit interaction will be explored through measurements in parallel magnetic field searching for signatures of first order transition and irreversibility. In addition to transport measurements, mesoscopic effects near the transition will be explored using novel techniques including scanning tunneling potentiometry and Kerr microscopy. The proposed work is expected shed new light on the nature of quantum phase transitions in reduced dimensions, as well as impact the understanding of the material science of amorphous superconducting films, and the development of new methodologies using novel measurements techniques. The program involves graduate students in this area of great interest to fundamental physics and future applications.

非技术抽象量化相变继续吸引强烈的理论和实验兴趣。这样的过渡 - 在哈密顿量中改变外部参数会引起从一个量子基态到另一个量子基本状态的过渡，从根本上讲是不同的 - 已被调用以了解许多电子系统中的实验数据，并分析更具挑战性的量子现象。作为量子计算的局限性。量子相变的范式一直是二维膜中绝缘体过渡的超导体。发现这种过渡具有多种实现，具体取决于所用材料的内在特性。控制膜的超导性，混乱或维度的强度将影响过渡的性质，该过渡的性质是通过诸如温度和磁场等外部参数的变化来访问的。该奖项支持一个项目，旨在探索无定形MGB2电影和多层型绝缘过渡的超导体。该系统的独特性在于能够控制非常宽的范围内超导性的强度，控制该疾病，并制造双层和多层。但是，更独特的是，由于镁和硼的轻盈，旋转轨道相互作用可能是任何薄膜超导体中最低的，这为我们提供了研究其对过渡影响的新机会。预计拟议的工作将影响多个领域的科学，包括在降低的尺寸中阐明量子相变的性质，更好地理解非晶性超导膜的材料科学以及使用新方法的新方法开发新方法。该计划涉及该领域中对物理和未来应用的研究生。技术抽象研究二维超导体的相图已与寻找新材料密切相关。对于每个材料系统，突出显示了一组不同的属性。多年来，NSF的支持可以优化多种材料，以研究一般的薄超导膜，尤其是绝缘体转变（SIT）的超导体。其中包括可以发现“金属阶段”的无定形膜膜，无定形的Inox膜，可以研究强烈的疾病制度，以及最近的无定形mgb2膜，除了具有Moge和Moge和Inox参数重叠的异形，还提供一种以控制自旋轨道相互作用的形式的新旋钮。一种新的新型技术，用于制造无定形MGB2/MGO的多层，可以进一步探索维度效应。该奖项支持一个探索MGB2模型系统提供的丰富物理学的项目。将进行实验以研究MGB2薄膜的垂直磁场中的各种类型的双层（例如接近系统）和多层。将特别注意量子熔化在坐姿点附近的效果。低自旋轨道相互作用的表现将通过平行磁场中的测量进行探索，以搜索一阶过渡和不可逆性的签名。除了运输测量值外，还将使用包括扫描隧道电位测量和KERR显微镜在内的新技术来探索过渡附近的介观效应。预计所提出的工作为降低的尺寸中的量子相变的性质提供了新的启示，并影响了对无定形超导膜的材料科学的理解，以及使用新型测量技术开发新方法。该计划涉及该领域的研究生，对基本物理和未来应用非常感兴趣。