Correlated magnets and superconductors explored using muon-spin rotation

植入的μ子为量子材料提供了独特的局域视角。通过测量植入的μ子自旋在局部磁场中的旋转，而局部磁场又是由附近磁矩产生的偶极场产生的，人们可以遵循磁序参数作为温度的函数。如果存在一定范围的μ子位置，该技术可以提供有关内部磁场分布的信息。即使在磁转变温度以上，测量的μ子自旋弛豫也可以提供有关磁波动和自旋动力学的信息。在超导体中，这项技术特别有价值，因为测量的内部场分布可以让我们推断配对机制。然而，这种技术有一个基本的局限性，即缺乏对μ子植入位置的了解和μ子对宿主扰动的不确定性。我们发现这个问题可以通过电子结构计算来解决，使用我们开发的一种技术，我们称之为“DFT+mu”，包含μ子的密度泛函理论。这种哲学博士。项目将包括在新磁体和超导体上使用μ子的实验，以及由DFT+mu方法激发的研究。目的是进一步加深我们对磁性和超导材料的理解，同时也通过对介子位的性质获得新的见解来扩展介子自旋旋转技术。

Implanted muons give a unique local perspective on quantum materials. By measuring the rotation of the implanted muon spin in the local magnetic field, which in turn results from the dipolar field arising from nearby magnetic moments, one can follow the magnetic order parameter as a function of temperature. If there are a range of muon sites the technique can provide information about the internal magnetic field distribution. Even above the magnetic transition temperature, the measured relaxation of the muon spin can provide information about magnetic fluctuations and spin dynamics. In superconductors the technique is particularly valuable because the measured internal field distribution can allow us to infer the pairing mechanism. However, there is a fundamental limitation of this technique which comes from the lack of knowledge of the implantation site of the muon and the uncertainty about the muon's perturbation of its host. We have found that this problem can be addressed using electronic-structure calculations using a technique we have developed which we call "DFT+mu", density functional theory with an included muon. This D.Phil. project will involve experiments using muons on new magnets and superconductors, as well as investigations motivated by the DFT+mu method. The aim is to further our understanding of the magnetic and superconducting materials, but also to extend the muon-spin rotation technique by gaining new insights into the nature of muon sites.