Low energy electrodynamics of strongly interacting disordered systems: quantum phase transitions and many-body localization

强相互作用无序系统的低能电动力学：量子相变和多体局域化

• 批准号: 1508645
• 负责人: Norman Armitage
• 金额: $ 36.76万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1508645&HistoricalAwards=false
• 关键词: Low; energy; electrodynamics; strongly; interacting

Nontechnical description:It is hardly an exaggeration that most of what we know about physical systems comes from their response to perturbations at their characteristic frequencies. For instance, the fundamental tone of a plucked violin string depends on the length of the string, the tension in it, and its thickness. This is true from the acoustics of a violin to the energies of atoms. Unfortunately the natural frequency scales of many solid materials fall in a spectral range, which has been prohibitively difficult to access technically until recently. This project takes advantage of recent dramatic technical advances in THz and microwave spectroscopy to characterize the natural frequency scales of disordered solids. Material systems like superconductors, which can conduct electricity without resistance and various insulating states are being studied. The investigations performed herein give essential information to develop new materials with important technological implications. These technological developments are coupled to a broad initiative in education and outreach. The work is of particular educational value to students owing to the low frequency electrodynamics techniques that are employed and which are finding broad application in research and private industry. Public outreach activities in the form of the Johns Hopkins Physics Fair is also being realized. Technical description:Interactions, disorder, and their interplay is a central theme of modern condensed matter physics. This project is exploring two areas of intense recent interest where strong interactions and disorder conspire to create exotic low temperature states of quantum matter: the 2D superconductor insulator quantum phase transition and the phenomena of ``many-­body localization". They are being investigated by a number of novel low energy electrodynamic probes available in the PI's group. The 2D superconductor-­insulator transition (2D SIT) is a paradigmatic example of a quantum phase transition (QPT) -­ a topic of much interest in the condensed matter physics. Recent advances in low temperature microwave spectroscopies are being exploited to provide the first true dynamic information about this phase transition in thin superconducting (InO) films. The phenomena of many-­body localization is also being investigated. Recently Basko, Aleiner, and Altshuler demonstrated that for systems with strong enough disorder, localization can prevent energy or particle transport, so that the system fails to equilibrate and to be its own heat bath. This implies that (in the absence of delocalized degrees of freedom like phonons) there should be a finite temperature localization transition. We are investigating the relaxation dynamics of both electron glass systems and disordered Ising chains and among other things looking for changes in the THz relaxation as function of optical pump parameters.

非技术描述：毫不夸张地说，我们对物理系统的大部分了解都来自于它们对其特征频率的扰动的响应，例如，拨动的小提琴弦的基音取决于弦的长度、张力。从小提琴的声学到原子的能量都是如此。不幸的是，许多固体材料的固有频率范围都落在一个光谱范围内，直到最近这个项目才在技术上实现这一范围。近期的优势太赫兹和微波光谱学在表征无序固体的固有频率尺度方面取得了巨大的技术进步，这些材料系统可以无电阻地导电，并且正在研究各种绝缘状态，本文中进行的研究为开发具有重要意义的新材料提供了必要的信息。这些技术的发展与教育和推广方面的广泛举措相结合，由于所采用的低频电动力学技术在研究和私营行业中得到了广泛应用，因此这项工作对学生具有特殊的教育价值。形式为约翰霍普金斯大学物理博览会也正在实现。 技术描述：相互作用、无序及其相互作用是现代凝聚态物理学的中心主题，该项目正在探索最近引起强烈兴趣的两个领域，在这两个领域中，强相互作用和无序共同创造了奇异的低值。量子物质的温度状态：二维超导绝缘体量子相变和“多体局域化”现象。PI 小组中可用的许多新型低能电动探针正在对它们进行研究。二维超导-绝缘体转变 (2D SIT) 是量子相变 (QPT) 的一个典型例子，这是凝聚态物理中备受关注的一个话题，人们正在利用低温微波光谱学的最新进展来提供第一个真正的动态信息。最近，Basko、Aleiner 和 Altshuler 证明了对于超导 (InO) 薄膜中的这种相变，对于具有足够强度的系统。无序，局部化可以阻止能量或粒子传输，从而使系统无法平衡并成为其自己的热浴，这意味着（在没有像声子这样的离域自由度的情况下）应该存在有限的温度局部化转变。正在研究电子玻璃系统和无序伊辛链的弛豫动力学，以及寻找太赫兹弛豫随光泵参数变化的变化。