Quantum Phase Transitions of Correlated Electrons and Atoms

相关电子和原子的量子相变

• 批准号: 0757145
• 负责人: Subir Sachdev
• 金额: $ 43.5万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0757145&HistoricalAwards=false
• 关键词: Quantum; Phase; Transitions; Correlated; Electrons

TECHNICAL SUMMARY:This award supports theoretical research and education aiming to understand materials in the vicinity of quantum phase transitions. Quantum phase transitions occur across critical points where there is a qualitative change in the quantum mechanical ground state. By tuning parameters, such as carrier concentration, magnetic field strength, or pressure, new quantum phases with novel physical properties have been discovered. The PI aims to carry out a variety of theoretical studies motivated by remarkable experimental progress in Cu-based transition metal oxides, in organic compounds, in optical lattices of ultracold atoms, and in graphene. These examples include novel insulating spin gap states with evidence for valence bond solid order, one of which becomes a superconductor under applied pressure. The PI will study transitions between such phases which are metals, insulators, or superconductors. Many of these phases are characterized by exotic topological orders. The PI will study the response of such phases to impurities and other local perturbations, to make contact with nanoscale experimental probes such as the scanning tunneling microscope. The PI will also pursue investigations in the `quantum critical' region, found at intermediate temperatures near a quantum critical point, which has applications to observations in the underdoped cuprates, in thin superconducting films and wires, and in graphene. The PI has developed new tools to address quantum criticality by adapting advances in the string theory description of black holes. He plans to expand the reach of such tools to a wider class of strongly interacting many-body systems.This award supports activities beyond the research thrust, including connections with the global scientific community through visiting post-doctoral fellows, supported by fellowships from their home countries, the preparation of a more accessible second edition of the PI?s book ?Quantum Phase Transitions? which summarizes key ideas behind this research for graduate students.NON-TECHNICAL SUMMARY:This award supports theoretical research and education that aims to predict new states of matter and understand transformations among them and known states of matter. The research focuses on transformations that occur at the absolute zero of temperature in response to changes in a physical parameter such as pressure or the strength of interaction between electrons. Unlike more familiar transformations, like water to steam, these transformations of phase are not a consequence of changes in temperature. Rather they are a consequence of Heisenberg?s uncertainty principle, a cornerstone of quantum mechanics. These quantum phase transitions may be realized between new states of matter that may exist in high temperature superconductors, a class of organic conductors, systems of cold atoms trapped by light, and more. The PI?s work utilizes advanced theoretical techniques that benefit from ?cross-pollination? with branches of physics that study subatomic particles and the origins of gravity.This award supports activities beyond the research thrust, including connections with the global scientific community through visiting post-doctoral fellows, supported by fellowships from their home countries, the preparation of a more accessible second edition of the PI?s book ?Quantum Phase Transitions? which summarizes key ideas behind this research for graduate students.

技术摘要：该奖项支持旨在了解量子相变附近材料的理论研究和教育。量子相变发生在量子力学基态发生质变的临界点。通过调整载流子浓度、磁场强度或压力等参数，已经发现了具有新颖物理性质的新量子相。该项目负责人旨在以铜基过渡金属氧化物、有机化合物、超冷原子光学晶格和石墨烯方面取得的显着实验进展为动力，开展各种理论研究。这些例子包括新颖的绝缘自旋间隙态，具有价键固序的证据，其中之一在施加压力下变成超导体。 PI 将研究金属、绝缘体或超导体等相之间的转变。其中许多相都具有奇异的拓扑顺序。 PI 将研究这些相对杂质和其他局部扰动的响应，以与扫描隧道显微镜等纳米级实验探针进行接触。 PI还将在量子临界点附近的中间温度下发现的“量子临界”区域进行研究，该区域可应用于欠掺杂铜酸盐、薄超导薄膜和导线以及石墨烯中的观测。 PI 开发了新工具，通过采用黑洞弦理论描述的进步来解决量子临界问题。他计划将此类工具的应用范围扩大到更广泛的强相互作用的多体系统。该奖项支持研究重点之外的活动，包括通过访问博士后研究员与全球科学界建立联系，并获得本国奖学金的支持，准备更容易理解的 PI 著作《量子相变》第二版。它为研究生总结了这项研究背后的关键思想。非技术摘要：该奖项支持旨在预测新的物质状态并理解它们与已知物质状态之间的转变的理论研究和教育。 该研究的重点是在绝对零温度下发生的转变，以响应压力或电子之间相互作用强度等物理参数的变化。与更常见的转变（例如水到蒸汽）不同，这些相变不是温度变化的结果。相反，它们是海森堡不确定性原理（量子力学的基石）的结果。这些量子相变可以在高温超导体、一类有机导体、光捕获的冷原子系统等中存在的新物质状态之间实现。 PI 的工作利用了受益于“异花授粉”的先进理论技术。该奖项支持研究重点之外的活动，包括通过访问博士后研究员与全球科学界建立联系，并在其本国的奖学金的支持下，编写更容易理解的 PI 书籍“量子相变”第二版。其中为研究生总结了这项研究背后的关键思想。