几何无序对自旋阻挫体系中量子态的调控

The goal of this project is to realize and manipulate the exotic quantum states in frustrated magnets by means of geometric disorder. By using a real-space slave boson theory combined with quantum Monte Carlo simulations, we will study the effects of geometric disorder on the thermodynamics and spin excitations of several typical frustrated spin models, for example, Heisenberg model on triangular lattice. We will obtain the criterion of realizing the exotic quantum (disordered) states, understand the nature of these states, and investigate the properties of phase transitions associated with these states. We propose the connection between our theoretical results and real materials. Hope that our research generates international impact. In the meantime, we will train two to three graduate students through this project.

本项目将探索以几何无序作为一种新的手段来实现与调控自旋阻挫体系中的奇异量子态。针对几类典型的自旋阻挫模型，如三角晶格上的海森堡模型等，发展并应用实空间隶玻色子理论与量子蒙特卡洛模拟等方法研究几何无序对体系热力学性质与自旋激发谱的影响。得到几何无序诱导实现奇异量子无序态的条件，从准粒子局域化的角度理解这些量子无序态的内在结构，并研究与这些量子态相关的相变的性质。结合实际材料中探讨本项目涉及到的奇异量子态及其相关相变在材料中实现的可能性与条件。希望通过本项目中新的研究视角与理论方法，促进自旋阻挫体系奇异量子效应的前沿研究，产生一批具有国际影响的研究成果，同时培养2-3名高质量的研究生。

本项目针对若干自旋阻挫体系研究了无序对体系基态与激发态的调控作用，.取得了一系列研究结果：发展了适用于S=1/2与S=1等量子自旋阻挫体系的隶粒子理论；研究了方格子S=1的J1-J2-K1-K2模型中反铁四极矩与向列涨落对体系自旋激发谱的影响；提出并研究了针对YbAlO3的反铁磁海森堡-伊辛模型在磁场下的相图，发现了无序涨落导致的非公度自旋密度波态。在项目支持下发表学术论文19篇。这些研究成果有效推动了量子多体理论技术的发展，促进了自旋阻挫体系新奇量子效应的前沿研究。项目期间培养了2名博士与4名硕士。