Superconductor-Insulator Transitions

超导体-绝缘体转变

• 批准号: 1704456
• 负责人: Allen Goldman
• 金额: $ 51万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1704456&HistoricalAwards=false
• 关键词: Superconductor; Insulator; Transitions

Non-Technical Abstract:This research supports the experimental investigation of superconductor-insulator transitions of ultrathin films of elements and compounds. Understanding their nature is important, in part because of their role in high temperature superconductivity. They are the simplest examples of an important paradigm of contemporary condensed matter physics, continuous quantum phase transitions, which in contrast with thermal transitions, occur at zero temperature, but have measurable signatures at nonzero temperatures, which are used to characterize them. In the case of the superconductor-insulator transition, the ground state is changed in response to the variation of an external parameter of the system, such as parallel or perpendicular magnetic field, disorder, or carrier density. Among other systems exhibiting quantum phase transitions are 4He adsorbed on random substrates, two-dimensional electron gases, numerous complex strongly correlated electron materials, and configurations of cold atoms, which can be effectively used to model many condensed matter phenomena. The study of superconductor-insulator transitions requires advanced tools of experimental science such as film growth, nanofabrication and ultra-low temperature measurement techniques. This project supports the training of both Ph.D. and undergraduate students that is excellent preparation for a scientific career. The primary outreach activity of the PI is the teaching of freshman seminars.Technical Abstract:The research is directed at identifying the mechanisms associated with a variety of superconductor-insulator transitions involving different materials and tuning parameters. It involves four distinct investigations. The first investigation is an attempt to see whether a superconductor-insulator transition in a disordered thin film can be systematically tuned by dissipation provided by a tunable, proximate two-dimensional electron gas. The second investigation is the measurement of the charge-density dependence of films of the super-electron density using an AC technique, over a range of carrier concentrations of films of the oxygen-enriched compound, La2CuO4+x (LCO) which are electrostatically doped using ionic liquids. The third thrust is the measurement of the out-of-equilibrium, current noise spectral density near the superconductor-insulator transition of quench-deposited metal films, and the fourth direction of research is the study of the perpendicular-field tuned superconductor-insulator transition of quench-deposited metal films with the goal of determining whether the limiting resistance at the quantum critical point is the quantum resistance for pairs, and whether there is a Hall insulator in these materials, as is apparently present in the case of compounds such as indium oxide.

非技术摘要：这项研究支持了元素和化合物的超导体-绝缘体转变的实验研究。 了解它们的性质很重要，部分原因是它们在高温超导中的作用。它们是当代凝聚态物理学的一个重要范例的最简单的例子，连续量子相变，与热相变相反，发生在零温度下，但在非零温度下有可测量的签名，用于表征它们。 在超导体-绝缘体转变的情况下，基态响应于系统的外部参数的变化而改变，例如平行或垂直磁场、无序或载流子密度。在其他表现出量子相变的系统中，有吸附在随机衬底上的4 He，二维电子气，许多复杂的强相关电子材料和冷原子的配置，它们可以有效地用于模拟许多凝聚态现象。 超导体-绝缘体转变的研究需要先进的实验科学工具，如薄膜生长，纳米纤维和超低温测量技术。该项目支持培养博士和博士生。和本科生，这是一个很好的科学生涯的准备。 PI的主要外展活动是新生研讨会的教学。技术摘要：该研究旨在确定与各种超导体-绝缘体转变相关的机制，涉及不同的材料和调谐参数。它涉及四个不同的调查。第一个调查是试图看看是否可以系统地调谐由一个可调的，接近二维电子气提供的耗散在无序薄膜的超导体-绝缘体转变。第二项调查是测量的电荷密度依赖性的超电子密度的薄膜，使用AC技术，在一个范围内的载流子浓度的膜的富氧化合物，La 2CuO 4 +x（LCO），这是静电掺杂使用离子液体。 第三个方向是测量淬火沉积金属膜的超导体-绝缘体转变附近的非平衡电流噪声谱密度，第四个研究方向是研究淬火沉积金属膜的磁场调谐超导体-绝缘体转变，目的是确定量子临界点处的极限电阻是否是对的量子电阻，以及在这些材料中是否存在霍尔绝缘体，如在诸如氧化铟的化合物的情况中明显存在的那样。

项目成果

Quantum Superconductor-Metal Transitions in the Presence of Quenched Disorder

• DOI: 10.1007/s10948-019-05250-1
• 发表时间: 2020-01
• 期刊: Journal of Superconductivity and Novel Magnetism
• 影响因子: 1.8
• 作者: Nicholas A. Lewellyn;Ilana M. Percher;J. Nelson;J. García‐Barriocanal;I. Volotsenko;A. Frydman;T. Voj

Infinite-randomness fixed point of the quantum superconductor-metal transitions in amorphous thin films

• DOI: 10.1103/physrevb.99.054515
• 发表时间: 2018-09
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Nicholas A. Lewellyn;Ilana M. Percher;J. Nelson;J. García‐Barriocanal;I. Volotsenko;A. Frydman;T. Voj