Probing the nature of excitations in spin-orbit-coupled materials from first principles

理解奇异磁态的本质，如自旋液体及其激发是一项具有挑战性的任务。困难的两个主要来源是：(i)缺乏对所建议材料实现的实验的完整微观描述，以及（ii）这样的状态在自然界中很少见的事实。关于后者，近年来，自旋轨道耦合量子磁体已经成为与基塔耶夫模型相关的这些非常规状态的可能宿主。该项目旨在通过探索自旋轨道耦合量子磁体的性质、它们的激发和相应的实验响应，特别强调热输运和光谱测量，为上述第一个挑战做出贡献。这将通过第一性原理方法和数值多体技术（有限系统的精确对角化，各种平均场方法以及半经典和微扰方法）的结合来实现。我们将首先通过第一性原理、密度泛函理论研究和投影方法推导出合适的伪自旋哈密顿量，并将其作为探索的起点，利用合适的多体工具，将响应函数与实验测量结果进行比较。我们还将通过从第一性原理设计具有调谐自旋相互作用的材料平台来显示可能的奇异磁相，从而为上述第二个挑战做出贡献。

Understanding the nature of exotic magnetic states such as spin liquids and their excitations is a challenging task. Two main sources of difficulty are (i) a lack of a full microscopic description of experiments on suggested materials' realizations, and (ii) the fact that such states are rare in nature. Regarding the latter, in recent years spin-orbit-coupled quantum magnets have emerged as possible hosts of these type of unconventional states in relation to the Kitaev model.This project aims at contributing to the first challenge above by exploring the nature of spin-orbit-coupled quantum magnets, their excitations and the corresponding experimental response, with special emphasis on thermal transport and spectroscopic measurements. This will be pursued by a combination of first principles methods and numerical many-body techniques (exact diagonalization of finite systems, various mean field approaches as well as semiclassical and perturbative methods). We will first derive via first principles density functional theory studies and projection methods the appropriate pseudo-spin Hamiltonians and consider them as starting point to explore, with suitable many-body tools, response functions to compare with experimental measurements.We will also contribute to the second challenge above by designing from first principles material platforms with tuned spin interactions to manifest possible exotic magnetic phases.