Room-Temperature Topological Phase Transition in Quasi-One-Dimensional Material Bi4I4
Room-Temperature Topological Phase Transition in Quasi-One-Dimensional Material Bi4I4
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DOI：
10.1103/physrevx.11.031042
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发表时间：
2021-08-24
影响因子：
12.5
通讯作者：
Yi, Ming
中科院分区：
文献类型：
--
作者：
Huang, Jianwei;Li, Sheng;Yi, Ming
准一维(1D)材料为表征和调整拓扑相提供了一个优越的平台，原因有二：(I)存在多个可解理表面，这使得能够更好地实验识别拓扑分类；(Ii)与高维晶体结构相比，对诸如应变等扰动的响应更强，用于调整拓扑相。在这篇文章中，我们提出了准一维材料Bi4I4的室温拓扑相变的实验证据，这种相变是通过弱耦合链的两个不同堆积顺序之间的一级结构相变来实现的。利用两个天然可解理表面的高分辨角度分辨光电子能谱，我们确定高温β相是第一个弱的拓扑绝缘体，在(100)面有两个无间隙的狄拉克锥，在(001)面没有狄拉克交叉，而在低温a相，(100)面的拓扑表面态打开了一个缺口，这与最近关于高阶拓扑绝缘体的理论预测一致，超出了已建立的包含无间隙铰链态的拓扑材料数据库的范围。我们的结果不仅证实了一阶和二阶拓扑绝缘体之间罕见的拓扑相变，而且为探索前所未有的物理现象建立了一个新的准一维材料平台。
Quasi-one-dimensional (1D) materials provide a superior platform for characterizing and tuning topological phases for two reasons: (i) existence for multiple cleavable surfaces that enables better experimental identification of topological classification and (ii) stronger response to perturbations such as strain for tuning topological phases compared to higher dimensional crystal structures. In this paper, we present experimental evidence for a room-temperature topological phase transition in the quasi-1D material Bi4I4, mediated via a first-order structural transition between two distinct stacking orders of the weakly coupled chains. Using high-resolution angle-resolved photoemission spectroscopy on the two natural cleavable surfaces, we identify the high-temperature beta phase to be the first weak topological insulator with two gapless Dirac cones on the (100) surface and no Dirac crossing on the (001) surface, while in the low-temperature a phase, the topological surface state on the (100) surface opens a gap, consistent with a recent theoretical prediction of a higher-order topological insulator beyond the scope of the established topological materials databases that hosts gapless hinge states. Our results not only identify a rare topological phase transition between first-order and second-order topological insulators but also establish a novel quasi-1D material platform for exploring unprecedented physics.