Developing the fermionic quantum order by disorder approach to understanding novel quantum phases.

通过无序方法开发费米子量子序来理解新的量子相。

• 批准号: 1904745
• 金额: --
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-1904745
• 关键词: Developing; fermionic; quantum; order; disorder

In recent years the Green group has developed a new approach to understanding how quantum fluctuations can induce new phases of electrons in solids with possibly useful properties. This approach - known as fermionic quantum order by disorder is largely analytical providing a good qualitative account of a range of quantum phenomena. Whilst analytically tractable models play an important role in the qualitative understanding of new phenomena, sometimes numerically precise predictions are needed - particularly when guiding experiment through a delicate balance of competing possibilities. Presently, the calculation of fluctuation-induced effects, such as superconductivity, is carried out in parallel with ab initio band structure calculations; the latter providing spin susceptibilities that are used in field theoretical Eliashberg type equations. It would be appealing if these calculations could be performed in concert. QOBD suggests a natural way to do so. It sits nicely within the a framework , which places DFT, DMFT and Baym-Kadanoff theory in a unified context. Our formulation of QOBD is essentially a restriction of Baym-Kadanoff theory where the variational parameter - the Green's function - is itself characterised by a restricted set of parameters. We aim to incorporate QOBD into DFT, enabling us to study density wave, electron nematic, and spatially modulated magnetic order, and superconductivity all within the same numerical framework. To pursue this possibility, Prof Chris Pickard (CJP Cambridge) and AGG will combine their complementary numerical and analytical skills in joint supervision of the PhD project. This project will be a pilot study to asses the viability of this approach. No immediate commercialisation is expected.

近年来，格林小组开发了一种新的方法来理解量子涨落如何在具有可能有用特性的固体中诱导电子的新相位。这种被称为费米量子有序无序的方法主要是分析性的，为一系列量子现象提供了良好的定性描述。虽然分析上易于处理的模型在定性理解新现象方面发挥着重要作用，但有时需要精确的数值预测——特别是在通过竞争可能性的微妙平衡指导实验时。目前，涨落效应（如超导性）的计算是与从头算能带结构计算并行进行的；后者提供了用于场论Eliashberg型方程的自旋磁化率。如果这些计算能够同时进行，那将是很有吸引力的。QOBD提出了一种自然的方法。它很好地放在一个框架内，将DFT， DMFT和Baym-Kadanoff理论放在一个统一的上下文中。我们的QOBD公式本质上是Baym-Kadanoff理论的一个限制，其中变分参数——格林函数——本身是由一组有限的参数表征的。我们的目标是将QOBD整合到DFT中，使我们能够在同一个数值框架内研究密度波、电子向列、空间调制磁序和超导性。为了实现这一可能性，Chris Pickard教授（剑桥CJP）和AGG将结合他们互补的数值和分析技能，共同监督博士项目。这个项目将是一项试验性研究，以评估这种方法的可行性。预计不会立即商业化。