量子自旋液体候选材料的缪子自旋弛豫研究

量子自旋液体是一种新奇的磁性物态。由于极强的量子涨落，直至零温都不会出现长程序。量子自旋液体的基态不能用序参量描述，并且缺少对称性破缺，因此该物态的实现打破朗道理论的范式。对于量子自旋液体的研究有助于理解高温超导的机理，并且可以被应用在量子计算和量子信息中。目前，尽管理论上有了长足的发展，但仍旧没有任何一个材料被证实为量子自旋液体。因此，探测和确认一个真正的量子自旋液体材料是当前的研究重点。缪子自旋弛豫是一个对磁场极为敏感的实验技术，被广泛应用于量子自旋液体候选材料的研究中。该技术可以观测基态中是否存在磁有序，测量系统中的涨落频率，这两点都是表征量子自旋液体的重要性质。本文简要介绍了量子自旋液体态和缪子自旋弛豫技术，回顾了近期在不同体系的量子自旋液体候选材料中的实验结果，特别是缪子自旋弛豫的成果。这些体系包括一维反铁磁海森堡链（苯甲酸铜），三角格子（YbMgGaO4，NaYbO2 和TbInO3），笼目格ZnCu3(OH)6Cl2 和 m3Sb3Zn2O14]，蜂窝状格子（Na2IrO3 和 α-RuCl3），以及烧绿石结构（Tb2Ti2O7，Pr2Ir2O7 和Ce2Zr2O7）。

Muon Spin Relaxation Studies on Quantum Spin Liquid Candidates

Quantum spin liquid is a novel magnetic state without long-range order even at zero temperature due to strong quantum fluctuations. The ground state of quantum spin liquid cannot be described by order parameters, and there is no symmetry breaking in this exotic state, which means that the realization of quantum spin liquid states will break through the paradigm of Landau’s theory. Studies on quantum spin liquid will be helpful for the understanding of the mechanism of high-temperature superconductivity and the application of quantum calculation and quantum information. Although there are many advances in the theory, no material is confirmed to be a real quantum spin liquid so far, making it important to realize a quantum spin liquid material and confirm its properties. Muon spin relaxation, a powerful technique that is extremely sensitive to magnetic fields, has been widely used in the study of quantum spin liquid candidates. Muon spin relaxation can observe whether there is long-range order in the ground state, and measure the fluctuation rate in the system, both of which are the basic properties of quantum spin liquid. This article gives a brief introduction to the quantum spin liquid state and muon spin relaxation technique. Then recent experimental works, especially muon spin relaxation experiments, on different systems, including one-dimensional antiferromagnetic Heisenberg chain (copper benzoate), triangular lattice (YbMgGaO4, NaYbO2 and TbInO3), kagomè lattice ZnCu3(OH)6Cl2 and Tm3Sb3Zn2O14], honeycomb lattice (Na2IrO3 and α-RuCl3) and pyrochlore lattice (Tb2Ti2O7, Pr2Ir2O7 and Ce2Zr2O7) are reviewed.