论文标题
反铁磁性拓扑绝缘子MNBI $ _2 $ TE $ _4 $中的自发表面崩溃和重建
Spontaneous Surface Collapse and Reconstruction in Antiferromagnetic Topological Insulator MnBi$_2$Te$_4$
论文作者
论文摘要
MNBI $ _2 $ te $ _4 $是一种反铁磁拓扑绝缘子，由于异国情调的量子现象和有前途的设备应用而刺激了强烈的利益。表面结构是了解MNBI2TE4的新型磁性和拓扑行为的决定因素，但其精确的原子结构仍然难以捉摸。在这里，我们发现在微妙的保护下被剥落的几层MNBI2TE4的自发表面崩溃和重建。倒塌的表面不是理想的隔层结构，而是重建了Mn掺杂的BI $ _2 $ _2 $ _3 $ _3 $ QUINTUPLE-LAYER和MN $ _X $ _X $ _X $ _Y $ _Y $ _Y $ _Y $ te te double te double-layer，介于两者之间。与第一原理计算相结合，这种自发的表面塌陷归因于剥落的表面中丰富的内在MN-BI抗酸盐缺陷和tellurium空位，这进一步得到了原地退火和电子辐照实验的支持。我们的结果阐明了对MNBI $ _2 $ te $ _4 $的复杂表面砖对应关系的理解，并提供了MNBI $ _2 $ TE $ _4 $ _4 $少数几层设备的表面相关量子测量的有见地的观点。
MnBi$_2$Te$_4$ is an antiferromagnetic topological insulator which stimulates intense interests due to the exotic quantum phenomena and promising device applications. Surface structure is a determinant factor to understand the novel magnetic and topological behavior of MnBi2Te4, yet its precise atomic structure remains elusive. Here, we discovered a spontaneous surface collapse and reconstruction in few-layer MnBi2Te4 exfoliated under delicate protection. Instead of the ideal septuple-layer structure in the bulk, the collapsed surface is shown to reconstruct as Mn-doped Bi$_2$Te$_3$ quintuple-layer and Mn$_x$Bi$_y$Te double-layer with a clear van der Waals gap in between. Combining with first-principles calculations, such spontaneous surface collapse is attributed to the abundant intrinsic Mn-Bi antisite defects and tellurium vacancy in the exfoliated surface, which is further supported by in-situ annealing and electron irradiation experiments. Our results shed light on the understanding of the intricate surface-bulk correspondence of MnBi$_2$Te$_4$, and provide insightful perspective of the surface-related quantum measurements in MnBi$_2$Te$_4$ few-layer devices.
