Microscopic Theory of High Temperature Superconductivity Induced by Electronic Fluctuations

电子涨落引起的高温超导微观理论

• 批准号: 1206298
• 负责人: Chandra Varma
• 金额: $ 33万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1206298&HistoricalAwards=false
• 关键词: Microscopic; Theory; Temperature; Superconductivity; Induced

TECHNICAL SUMMARYThis award supports theoretical research on a consistent microscopic theory of the extraordinary phenomena discovered in high temperature cuprate superconductors. Work done by the PI in the past two years suggests that d-wave superconductivity in cuprates comes from the quantum-critical fluctuations of the time-reversal order parameter discovered in the pseudogap region of the phase diagram and their derived coupling to fermions. In this project, the PI will work on providing definitive evidence for this suggestion by analyzing high resolution laser-angle-resolved-photoemission-spectroscopy to determine (i) the absolute magnitudes and the momentum and frequency dependence of the spectrum of fluctuations, and (ii) their coupling to fermions and variation for a range of dopings and critical temperatures. The expected outcome is the formulation of a fundamental and testable theory of the pseudo gap. In addition to this main theme, the PI and his group will undertake two new investigations on related problems: (1) Solution of Eliashberg equations for superconductivity induced by gaussian quantum-critical fluctuations, which are expected to yield results in variance with the Bardeen-Cooper-Schieffer type formulas for the energy gap, critical temperature, and thermodynamic quantities, and (2) Derivation of the multiple Higgs or amplitude modes expected in d-wave superconductors.This award also supports the education and training of a postdoctoral research associate and a graduate student in condensed matter theory. The PI will continue his active participation and mentoring activities under the University of California Leadership Excellence in Advanced Degrees and Mentoring Summer Research Internship programs. He will also participate in the Early Academic Outreach Program at this institution targeting high school students by providing various lectures and demonstrations. NON-TECHNICAL SUMMARYThis award supports theoretical research on a consistent microscopic theory of the extraordinary phenomena discovered in high temperature cuprate superconductors. These are materials discovered in the late 1980s that conduct electricity without any dissipation (no resistance, no energy loss) when they are cooled below certain critical temperatures. Even though the critical temperatures necessary for these materials to superconduct are significantly below the room temperature, they are still much higher compared to the critical temperatures of ordinary superconductors (which are close to absolute zero). Furthermore, a theory formulated in the late 1950s that explains the microscopic mechanism of superconductivity in ordinary superconductors is not adequate to explain the mechanism and physical properties of high temperature cuprate superconductors. Even though it has been 25 years since the discovery of high temperature superconductivity and many theories have been proposed, a consistent microscopic theory that explains all properties of cuprate superconductors is still missing. For the last several years, the PI and his group have been working on a theory that is consistent with most of the experimental findings. In this project, the PI will work on providing definitive evidence for his theory by analyzing the latest high resolution spectroscopy experiments. The expected outcome is the formulation of a fundamental and testable theory of an important part of the phase diagram of the cuprate superconductors. This award also supports the education and training of a postdoctoral research associate and a graduate student in condensed matter theory. The PI will continue his active participation and mentoring activities under the University of California Leadership Excellence in Advanced Degrees and Mentoring Summer Research Internship programs. He will also participate in the Early Academic Outreach Program at this institution targeting high school students by providing various lectures and demonstrations.

该奖项支持对高温铜氧化物超导体中发现的异常现象的一致微观理论的理论研究。PI在过去两年中所做的工作表明，铜酸盐中的d波超导电性来自于在相图的赝能隙区域发现的时间反转序参数的量子临界波动及其衍生的与费米子的耦合。在这个项目中，PI将通过分析高分辨率激光角分辨光电子能谱来确定（i）波动谱的绝对幅度和动量和频率依赖性，以及（ii）它们与费米子的耦合以及掺杂和临界温度范围内的变化，为这一建议提供明确的证据。预期的结果是制定一个基本的和可检验的理论的伪差距。 除了这一主题外，PI及其小组还将对相关问题进行两项新的调查：（1）高斯量子临界涨落引起的Eliashberg方程的解，它将产生与能隙、临界温度和热力学量的Bardeen-Cooper-Schieffer型公式不同的结果，以及（2）在d波超导体中预期的多重希格斯或振幅模式的推导。该奖项还支持凝聚态理论的博士后研究助理和研究生的教育和培训。 PI将继续积极参与和指导加州大学高级学位卓越领导和指导夏季研究实习计划下的活动。他还将参加该机构针对高中生的早期学术外展计划，提供各种讲座和演示。 非技术总结该奖项支持在高温铜氧化物超导体中发现的异常现象的一致微观理论的理论研究。这些材料是在20世纪80年代末发现的，当它们冷却到特定的临界温度以下时，它们可以导电而没有任何耗散（没有电阻，没有能量损失）。尽管这些材料超导所需的临界温度明显低于室温，但与普通超导体的临界温度（接近绝对零度）相比，它们仍然要高得多。 此外，在20世纪50年代后期提出的解释普通超导体中超导性的微观机制的理论不足以解释高温铜酸盐超导体的机制和物理性质。 尽管高温超导性的发现已经有25年的历史了，并且已经提出了许多理论，但是仍然缺少一个能够解释铜氧化物超导体所有性质的一致的微观理论。在过去的几年里，PI和他的团队一直在研究一个与大多数实验结果一致的理论。在这个项目中，PI将通过分析最新的高分辨率光谱实验为他的理论提供明确的证据。 预期的结果是制定一个基本的和可测试的理论的一个重要组成部分的相图的铜酸盐超导体。该奖项还支持博士后研究助理和凝聚态理论研究生的教育和培训。 PI将继续积极参与和指导加州大学高级学位卓越领导和指导夏季研究实习计划下的活动。他还将参加该机构针对高中生的早期学术外展计划，提供各种讲座和演示。