CAREER: Probing an Emergent New Class of Electronic Liquid Crystals Using Synchrotron X-rays: Superconductors and Beyond

非技术摘要：从半导体到塑料，新材料已经彻底改变了我们的生活。 例如，液晶已经改变了我们显示和传输信息的方式。 然而，这些进展是在我们对这些材料的性质有了了解之后才发生的，这些材料具有液体和固体的性质，以及它们所表现出的复杂相（分子排列）。 最近，我们对液晶理解的基础思想正在被应用于理解高温超导体等新材料的电子特性。 更详细地了解这些材料的特性将使它们能够针对电力传输和储能等应用进行优化。 在这个职业奖下，PI和他的学生将应用先进的X射线技术的独特组合来研究高温超导体和电荷密度波材料等系统，最终目标是建立对量子物质这些独特阶段的新理解。这项研究还包括一项围绕两个关键研究部分先进的x射线设备和超导体的教育和推广计划。前者是通过K-12辅导，本科生和研究生培训，在X射线设施和波士顿学院，课程开发，并为少数民族教师推广演示提供。一项以超导体为重点的推广计划，包括通过参与麻省理工学院博物馆举办的两个项目向公众提供讲座和磁悬浮演示，通过学校访问向地区初中和高中的学生提供讲座和演示，并通过组织小型培训讲习班向他们的教师提供讲座和演示。技术摘要：凝聚态物理学的一个中心主题是发现和理解量子物质的新相的出现。过去十年的研究已经使许多这样的相成为人们关注的焦点，包括电子液晶相。这些量子相的提出，实际上与经典流体的液晶相类似，因为它们在对称性破缺模式上有相似之处。电子向列相和近晶相是电子液晶的两大类主要研究对象。在这里，研究小组通过引入第三种已知的主要液晶相--打破长程手性对称性的胆固醇，寻求对这一迷人类比的进一步概括。在过渡金属二硫属化物和一些高Tc超导体中可能存在电子胆甾族化合物的初步迹象最近已经被实验发现，表明其在量子物质中与其双晶和近晶对应物一样普遍的潜力。为了研究这种有趣的可能性，首席研究员提出了一个全面的实验调查，在这个新兴的前沿与同步加速器X射线技术的独特组合的帮助。这些技术是元素特定的，并且可以通过不同的物理过程对不同的手性相关的物理量直接探测电子状态。他们的联合力量使现有的候选阶段能够被仔细检查到以前无法达到的深度，并为未来对其他凝聚态系统的探索奠定了基础。具体而言，铜酸盐超导体的拟议研究的目的是统一的理解的基础上，一个独特的手性角度的电荷排序现象-目前的重点高Tc领域。

Nontechnical Abstract:New materials, from semiconductors to plastics, have revolutionized our lives. Liquid crystals, for example, have transformed the way that we display and transmit information. However, these advances occurred only after we had developed an understanding of the properties of these materials, which share the properties of both liquid and solids, and the complex phases (arrangements of molecules) that they exhibit. Recently, the ideas that underlie our understanding of liquid crystals are being applied to understand the electronic properties of new materials such as high temperature superconductors. A more detailed understanding of the properties of these materials will allow them to be optimized for applications such as power transmission and energy storage. Under this CAREER award the PI and his students will apply a unique combination of advanced x-ray techniques to study systems such as high-temperature superconductors and charge density wave materials with an ultimate goal of establishing a new understanding of these unique phases of quantum matter. Integrated into the research is a plan for education and outreach centering around two key research components-advanced x-ray facilities and superconductors. The former is provided through K-12 mentoring, undergraduate and graduate training at x-ray facilities and Boston College, course development, and outreach presentations for minority faculty. An outreach plan focused on superconductors is planned that features both lectures and maglev demonstrations to be given to the general public through participation in two programs run by the MIT Museum, to the students of regional middle and high schools through school visits, and to their teachers through organizing small training workshops.Technical Abstract: A central theme of condensed matter physics is to discover and understand the emergence of novel phases of quantum matter. Research in the past decade has brought a number of such phases to the limelight, including electronic liquid crystal phases. These quantum phases were literally proposed in analogy to the liquid crystalline phases of classical fluids in terms of their similarities in the patterns of broken symmetry. Two classes of electronic liquid crystalline phases, the electron nematics and smectics, have been primarily focused on and attracted significant interest. Here, the research team seeks a further generalization of that fascinating analogy through the incorporation of the third known major liquid crystalline phase--the cholesterics that breaks long-range chiral symmetry. Initial indications for the possible existence of electron cholesterics in a transition-metal dichalcogenide and some high-Tc superconductors have recently been found experimentally, showing its potential of being as prevalent as its nematic and smectic counterparts in quantum matter. In order to look into this intriguing possibility, the principal investigator proposes a comprehensive experimental survey in this emerging frontier with the aid of a unique combination of synchrotron x-ray techniques. These techniques are element specific and can directly probe electronic states via different physics processes on different chirality-related physical quantities. Their joint force allows the existing candidate phases to be scrutinized to previously unattainable depth, and lays a foundation for future explorations on other condensed matter systems. Specifically, the proposed studies of cuprate superconductors aim for a unified understanding based on a unique chiral perspective of charge ordering phenomena - a current focus of the high-Tc field.