Theoretical Studies of Near-Critical, Strongly Interacting Electron Systems

技术概述：该奖项支持凝聚态物理领域的理论研究和教育，重点是表征量子临界点（QCP）附近的系统，其中流动费米子系统相对于自旋或电荷密度波顺序变得不稳定。在QCP附近，与几乎无间隙、过阻尼序参量场波动的相互作用破坏了电子在极低温度下的费米液体行为。同样的相互作用在非相干的非费米类液体激发之间产生配对。PI将重点研究铜超导体、流动铁磁体和重费米子材料。研究的最终目标是了解临界红外发散、莫特-海森堡物理、超导性以及有效相互作用中远程动态分量的存在之间的相互作用。建议的研究分为两类。首先，PI计划研究反铁磁不稳定性附近的流动费米子系统。PI旨在研究非相干费米子的超导性和非bcs配对成束缚自旋单重态之间的相互作用，以及当相互作用达到与费米子带宽相当时莫特-海森堡物理的出现。PI还提议测试电子掺杂铜酸盐的电子-玻色子模型，并寻找定性区分配对的磁性和声子机制的指纹。其次，PI计划研究波美拉丘克不稳定性附近的各向同性流动费米子系统。他的主要目标是确定非相干费米子的Eliashberg理论的稳定性，分析在什么条件下远程动态相互作用会破坏连续的QCP，研究可能的中间螺旋序参数构型，研究QCP附近的输运性质，特别是umklapp散射的作用。这项研究将涉及西澳大学研究生的培训和国际合作。智力优势：对QCP附近系统行为的分析具有重要的基础意义，具有很高的实验和理论价值。该研究将提高我们对QCP附近系统行为的认识，并将作为掺杂莫特绝缘体研究和近临界费米液体研究之间的桥梁。更广泛的影响：该奖项还支持学生在高级理论凝聚态物理和国际合作方面的培训。非技术总结：该奖项支持凝聚态物理领域的理论研究和教育。PI将研究一种有趣的相变它发生在绝对零度。物质不同状态之间的转变是由基本的量子力学原理驱动的，而不是由温度驱动的。这种相变可以深刻地影响电子在室温甚至更高温度下的行为。量子相变可能在理解高温超导现象和一类材料的其他性质方面发挥关键作用，其中电子之间的强相互作用导致它们的运动和电子物质的新状态的相关性。PI的研究旨在了解当材料接近量子相变时，电子的不寻常行为是如何导致超导性的。该奖项还支持学生在高级理论凝聚态物理方面的培训。

TECHNICAL SUMMARY:This award supports theoretical research and education in the area of condensed matter physics with a focus on characterizing systems near quantum critical points (QCP), where an itinerant fermion system becomes unstable with respect to either spin or charge density wave ordering. Near a QCP, the interaction with fluctuations of a near-gapless, overdamped order parameter field destroys Fermi liquid behavior of electrons down to very low temperatures.The same interaction gives rise to pairing between incoherent, non-Fermi-liquid-like excitations. The PI will focus on the cuprate superconductors, itinerant ferromagnets, and heavy fermion materials. The ultimate goal of the studies is to understand the interplay between infrared divergences at criticality, Mott-Heisenberg physics, superconductivity, and the presence of the long-range dynamic component in the effective interaction.The proposed studies are divided into two classes. First, the PI plans to study itinerant fermionic systems near an antiferromagnetic instability. The PI aims to study the interplay between the superconductivity and the non-BCS pairing of incoherent fermions into bound spin singlets, and the emergence of the Mott-Heisenberg physics once the interaction becomes comparable to the fermionic bandwidth. The PI also proposes to test an electron-boson model on electron-doped cuprates, and to search for the fingerprints that qualitatively distinguish between magnetic and phononic mechanisms for the pairing. Second, the PI plans to study isotropic itinerant fermionic systems near a Pomeranchuk instability. His main goals are to determine the stability of the Eliashberg theory for incoherent fermions, to analyze under what conditions long-range dynamic interaction destroys a continuous QCP, to study a possible intermediate spiral order parameter configuration, and to study transport properties near QCP, particularly the role of umklapp scattering.The research will involve the training of graduate students at UW and international collaborations. Intellectual merit: The analysis of the system behavior near a QCP is of fundamental importance and of high experimental and theoretical interest. The research will advance our knowledge of system behavior near a QCP, and will also serve as a bridge between the studies of doped Mott insulator and the studies of a near-critical Fermi liquid.Broader impact: This award also supports the training of students in advanced theoretical condensed matter physics and international collaboration.NON-TECHNICAL SUMMARY:This award supports theoretical research and education in the area of condensed matter physics. The PI will study an interesting kind of phase transition that occurs at the absolute zero of temperature. The transformation between different states of matter is driven by fundamental quantum mechanical principles rather then temperature. Such phase transitions can profoundly affect way electrons behave at temperatures as high as room temperature and possibly higher. Quantum phase transitions may play a key role in understanding the phenomenon of high temperature superconductivity and other properties of a class of materials where strong interactions among electrons lead to correlations in their motion and new states of electronic matter. The PI's research aims to understand how the unusual behavior of electrons that occurs when a material is close to a quantum phase transition can lead to superconductivity. This award also supports the training of students in advanced theoretical condensed matter physics.