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超薄膜超导膜的超导体 - 导管跃迁的实验研究。 理解它们的性质很重要，部分原因是它们在高温超导性中的作用。它们是当代冷凝物理物理学的重要范式的最简单例子，连续的量子相变（与热跃迁相反）发生在零温度下，但在非零温度下具有可测量的特征，用于表征它们。 在超导体 - 绝缘体跃迁的情况下，基态因系统外部参数的变化而改变，例如平行或垂直磁场，混乱或载体密度。在表现出量子相变的其他系统中，有4HE吸附在随机底物上，二维电子气体，许多复杂的复杂电子材料以及冷原子的构型，可有效地用于模拟许多凝结物质现象。 对超导体 - 绝缘体转变的研究需要实验科学的先进工具，例如膜的生长，纳米化和超低温度测量技术。该项目支持两家博士学位的培训。和本科生为科学职业做好了准备。 PI的主要外展活动是新生研讨会的教学。技术摘要：该研究旨在识别与涉及不同材料和调音参数的各种超导体 - 绝缘体转变相关的机制。它涉及四个不同的研究。首次研究是试图查看无序薄膜中的超导体 - 绝缘体过渡是否可以通过通过可调的，近距离的二维电子气体提供的耗散来系统地调节。第二个研究是使用AC技术在超级电子密度的膜的电荷密度依赖性上测量，在富含氧气富集化合物的一系列载流子浓度上，LA2CUO4+X（LCO）使用离子液体静电掺杂。 第三个推力是测量淬灭金属膜的超导体 - 导仪过渡附近的当前噪声频谱密度，研究的第四个方向是对垂直场调节的超导超导量临界器的量化量定量的量定量的量定量的研究，无论是在确定的量定量的范围内，是否是量化的量化性金属膜，是否是量化的量化性，是否是Quench降低了量化的范围，是否量化了量化的量化性金属膜，是否限制了量化性金属的范围。对这些材料中是否有霍尔绝缘子，如在诸如氧化酰胺等化合物的情况下显然存在的。

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