Quantum Phase Transitions in Unconventional Josephson Arrays

*非技术摘要*该奖项支持量子固态系统超低温物理的实验研究。本文主要研究了一类新型大阵列亚微米约瑟夫森结(超导体之间的隧道结)的设计、制备和表征。这项拟议研究的实施将有助于更好地理解无序系统物理学中的几个基本开放问题，包括与应用相关的广泛固态系统中的量子相变和玻璃效应。探索这些问题对于更好地理解量子系统退相干的起源具有重要的概念意义，并与实现固态元素的量子计算有关。参与这项研究的本科生和研究生都接受了先进实验技术方面的严格培训，并为在学术或工业环境中就业做好了准备。*技术摘要*拟议的研究集中在量子无序系统物理学中尚未解决的基本问题，包括有和没有长程相互作用的系统中的量子相变，出现的玻璃态行为，以及拓扑相的形成。这些物理问题将通过研究具有非传统几何结构的新型亚微米约瑟夫森结阵列中的电荷传输来解决：具有大量近邻元件的阵列，具有每个单位单元的大量结的阵列，以及具有非平凡拓扑的阵列。这些实验将对“玻色子”超导体-绝缘体转变的不同模型进行重要的测试，揭示在约瑟夫森阵列和超薄超导薄膜中经常观察到的神秘的“金属”相这一长期存在的问题，并解决电子玻璃物理学的基本公开问题。探索这些问题对于更好地理解低温下量子系统中消相干和噪声的来源具有重要意义。这项研究的实施促进了对本科生和研究生的培训，他们将接触到现代固态研究的最先进工具，并能够在学术或工业环境中追求职业生涯。

****NON-TECHNICAL ABSTRACT****This award supports experimental research in the ultra-low-temperature physics of quantum solid-state systems. The research focuses on the design, fabrication and characterization of a novel class of large arrays of sub-micron Josephson junctions (tunnel junctions between superconductors). Implementation of the proposed research will contribute to better understanding of several fundamental open problems in the physics of disordered systems, including the quantum phase transitions and glassy effects in a broad range of application-relevant solid-state systems. Exploration of these issues is conceptually important for better understanding of the origin of the decoherence of quantum systems, and relevant to the implementation of quantum computing with solid-state elements. The undergraduate and graduate students involved in this research receive rigorous training in advanced experimental techniques, and are prepared for careers in either an academic or industrial environment. ****TECHNICAL ABSTRACT****The proposed research focuses on the fundamental unsolved problems of the physics of quantum disordered systems, including quantum phase transitions in systems with and without long-range interactions, emergent glassy behavior, and formation of topological phases. These physical problems will be addressed by the study of charge transport in novel types of the arrays of sub-micron Josephson junctions with unconventional geometry: arrays with a large number of nearest-neighbor elements, arrays with a large number of junctions per unit cell, and arrays with non-trivial topologies. The experiments will provide an important test of different models of the "bosonic" superconductor-insulator transition, shed light on the long-standing issue of the enigmatic "metallic" phase frequently observed in Josephson arrays and ultra-thin superconducting films, and address fundamental open questions of the physics of electronic glasses. Exploration of these issues is conceptually important for better understanding of the origin of the decoherence and noise in quantum systems at low temperatures. Implementation of this research fosters training of both undergraduate and graduate students who will be exposed to the state-of-the-art tools of modern solid-state research, and can pursue careers in either an academic or industrial environment.