磁性阻挫材料中缺陷效应的第一性原理研究

Since Anderson’s proposal of applying resonating-valence-bond theory to high-temperature superconductors, frustrated magnetism has become an active field of research in condensed matter physics. The central role of frustration is to suppress the long-range order, which in turn spawns exotic phases, such as quantum spin liquid and unconventional superconductor, which are beyond the conventional Landau formalism based on the symmetry-breaking classification. In the past decade, several new families of materials with magnetic frustration have been discovered in experiment, shedding new lights on the development of the fundamental theory on strongly-correlated systems. However, it is not a trivial task to bridge the real-world materials with the abstract effective theory. In particular for a highly-frustrated system, the ground-state properties sensitively rely on the microscopic details of the material. Since the key energy scales associated with the ground state are small, defect effects, e.g. vacancy, substitution, domain boundary, carrier doping, play an important role. The proposal is to simulate several typical frustrated magnets within the formalism of first-principles calculation. By analyzing the electronic and magnetic properties around the defects, we aim to constructing effective models for further theoretical investigation, as well as providing guide for manipulating defects in experiment.

从Anderson提出高温超导的共振价键理论以来，磁性阻挫体系一直是凝聚态物理中的一个重要课题。阻挫的核心效应是压制长程序，从而使超越传统Landau对称破缺范式的新奇物态有可能得以演生出来。近十几年来，一系列存在磁性阻挫的新材料在实验上被合成，为相关理论的发展提供了新的素材。然而，一个重要的问题是，由于其中与基态相关的一些关键能量尺度通常都很小，包括空位、替换、畴界、载流子掺杂在内的各类缺陷效应都会扮演很重要的角色。本课题立足于以第一性原理计算为手段，模拟若干有代表性的磁性阻挫材料中的微观缺陷，分析其对于材料电子和磁性质的影响，进而为有效模型的建立和进一步的理论分析提供依据，为实验上如何调控缺陷提供指导。

从Anderson提出高温超导的共振价键理论以来，磁性阻挫体系一直是凝聚态物理中的一个重要课题。阻挫的核心效应是压制长程序，从而使超越传统Landau对称破缺范式的新奇物态有可能得以演生出来。近十几年来，一系列存在磁性阻挫的新材料在实验上被合成，为相关理论的发展提供了新的素材。然而，一个重要的问题是，由于其中与基态相关的一些关键能量尺度通常都很小，包括空位、替换、畴界、载流子掺杂在内的各类缺陷效应都会扮演很重要的角色。本课题通过融合多种第一性原理计算方法，模拟了Cu3Zn(OH)6Cl2, Cu3Zn(OH)6FBr, 1T-TaS2, FeSe, Ba2CuO4等多种磁性阻挫体系的重要性质，对于相关材料中的缺陷构型、缺陷对于核磁共振谱的影响、缺陷对于扫描隧道显谱的影响进行了细致的分析，为进一步的理论分析提供了重要的依据，也为实验上如何调控缺陷提供了有益的指导。