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****二维超导体相图的研究与寻找新材料密切相关。每个材料系统都会突出显示一组不同的属性。多年来，NSF 的支持使得各种材料得以优化，用于一般超导薄膜的研究，特别是超导体到绝缘体转变 (SIT) 的研究。其中包括允许发现“金属相”的非晶态 MoGe 薄膜、允许研究强无序状态的非晶态 InOx 薄膜、允许详细研究过渡附近霍尔效应的非晶态 TaNx 薄膜以及允许详细研究过渡附近的霍尔效应的非晶态 InOx 薄膜。 MgB2 薄膜除了与 MoGe、TaNx 和 InOx 的参数重叠外，还以控制自旋轨道相互作用的形式提供了新的旋钮。该项目探索超导体-绝缘体转变附近的丰富相图，重点关注中间的金属态。特别是，我们将集中精力了解金属背景（即耗散）下二维 SIT 的真实相图； 2D SIT 系统的电子微观结构是什么？我们能否从输运效应、霍尔效应和能斯特效应等实验中推断出各种长度尺度？并且，从金属膜上由有序金属点制成的人造膜开始，随着无序性的增加，这种方法的有效性范围是多少。拟议的工作预计将为降维中量子相变的本质提供新的线索，并影响对非晶超导薄膜材料科学的理解。****非技术摘要****量子相变继续吸引人们的关注。强烈的理论和实验兴趣。这种转变——改变哈密顿量中的外部参数会导致从一种量子基态转变到另一种根本不同的量子基态——已被用来理解许多电子系统中的实验数据，以及分析更具挑战性的量子现象，例如作为量子计算的局限性。量子相变的一个范例是二维薄膜中超导体到绝缘体的转变。人们发现这种转变有多种实现方式，具体取决于所用材料的固有特性。控制薄膜的超导性、无序性或维度的强度将影响转变的性质，这是通过温度和磁场等外部参数的变化来实现的。该奖项支持一个项目，探索非晶薄膜中超导体到绝缘体转变附近的一系列独特量子态，特别是非晶 MoGe、MgB2、InOx 和 TaNx。这套系统的独特性在于能够在非常广泛的参数范围内控制超导性和无序的强度，特别是允许访问我们小组首先识别出的人们知之甚少的普遍存在的金属态。该项目涉及对物理和未来应用非常感兴趣的这一领域的研究生。