Exploring Quantum Effects in Two-Dimensional Multilayered Superconductors

探索二维多层超导体中的量子效应

• 批准号: 1104547
• 负责人: Aharon Kapitulnik
• 金额: $ 5万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1104547&HistoricalAwards=false
• 关键词: Exploring; Quantum; Effects; Two; Dimensional

****Technical Abstract****Studies 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, amorphous TaNx that allowed for the detailed study of the Hall effect near the transition, and amorphous- MgB2 films which in addition to the overlap in parameters with MoGe, TaNx, and InOx, also provide a new knob in the form of controlling spin-orbit interaction. This project explores the rich phase diagram near the superconductor-insulator transition with emphasis on the intervening metallic states. In particular we will concentrate on understanding of what is the true phase diagram of two-dimensional SIT in the presence of a metallic background (i.e. dissipation); what is the electronic microstructure of a 2D SIT system; can we infer the various length scales from experiments such as transport, Hall and Nernst effects, etc.; and, starting from artificial films made of orderly metallic dots on a metal films, what is the range of validity of this approach as we increase disorder. The proposed work is expected to shed new light on the nature of quantum phase transitions in reduced dimensions and impact the understanding of the material science of amorphous superconducting films.****Non-Technical Abstract****Quantum 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 a series of unique quantum states near the superconductor to insulator transition in amorphous films, particularly amorphous-MoGe, MgB2, InOx and TaNx. The uniqueness of this set of systems is the ability to control the strength of superconductivity and disorder over a very wide range of parameters, and and in particular allow access to the poorly understood ubiquitous metallic states that have been first identified by our group. The program involves graduate students in this area of great interest to physics and future applications.

****技术摘要****对二维超导体的相图的研究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。 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, amorphous TaNx that allowed for the detailed study of the Hall effect near the transition, and amorphous- MgB2 films which in addition to the overlap in parameters with MoGe, TaNx, and InOx, also provide a new knob in the form of controlling自旋轨道相互作用。该项目探讨了超导体 - 绝缘体过渡附近的丰富相图，并着重于中间的金属状态。特别是，我们将集中精力理解在存在金属背景（即耗散）的情况下二维位置的真实相图。 2D SIT系统的电子微观结构是什么？我们可以从运输，霍尔和内尔特效应等实验中推断出各种长度尺度。而且，从金属膜上有序金属点制成的人造薄膜开始，随着我们增加混乱，这种方法的有效性范围是多少。预计拟议的工作将为降低的尺寸中的量子相变的性质提供新的启示，并影响对无定形超导膜的材料科学的理解。这种转变（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种量子态的过渡 - 从根本上不同 - 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，例如量子计算的局限性。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，旨在探索在无定形膜中绝缘体过渡的超导体过渡的一系列独特的量子状态，尤其是无定形 - 莫吉，MGB2，Inox和Tanx。这组系统的独特性在于能够在非常广泛的参数中控制超导性和混乱的强度，尤其是允许访问我们小组首先鉴定出的无处不在的金属状态。该计划涉及该领域的研究生，对物理和未来应用非常感兴趣。