通往量子自旋液体的新路径——Kitaev模型的材料实现

A new route to quantum spin liquids:material realization of the Kitaev model

Kitaev模型是一种建立在二维六角蜂窝状格子上的有效自旋为1/2的量子自旋液体模型。该模型可严格求解,具有拓扑序,分数化激发产生马约拉纳费米子与Z_(2)规范场,提供了对拓扑物理学与非易失性存储技术研究的新思路。区别于三角晶格与笼目格等材料中由于几何阻挫导致的量子自旋液体态,Kitaev量子自旋液体的形成来源于自旋空间中各向异性的Kitaev相互作用。近年来,在真实材料体系中寻找这种相互作用成为了实现量子自旋液体的新途径。其中,具有六角蜂窝状结构的莫特绝缘体α-RuCl_(3)被认为是众多候选材料中最具潜力的一种。文章将从实验角度出发,以α-RuCl_(3)为主要代表体系,介绍近年来在Kitaev量子自旋液体实验研究方面的重要进展,特别是以中子散射为主要手段对材料中与Kitaev量子自旋液体态相关的自旋激发态研究的结果。

The Kitaev model is a spin-1/2 model for a quantum spin liquid defined on a two-dimensional honeycomb lattice.It is an exactly solvable model,with topological order,fractionalized Majorana fermions and a Z2 gauge field,which provides a new direction for the study of topological physics,nonvolatile storage technology,and topological quantum computation.Different from the quantum spin liquid state induced by geometrical frustration in triangular and kagome lattices,the Kitaev quantum spin liquid is a consequence of the bond-dependent anisotropic Kitaev interactions.In recent years,searching for such interactions in real materials has become a new route to realize quantum spin liquids.Among the candidate materials,α-RuCl_(3),a Mott insulator with a honeycomb lattice,is believed to be the most promising.In this article we present the progress of experimental studies on Kitaev quantum spin liquids in recent years,with a focus on α-RuCl_(3).In particular,neutron scattering studies of the spin dynamics relevant to the Kitaev quantum spin liquid model will be highlighted.