Frolov Alexander S, Usachov Dmitry Yu, Fedorov Alexander V, Vilkov Oleg Yu, Golyashov Vladimir, Tereshchenko Oleg E, Bogomyakov Artem S, Kokh Konstantin, Muntwiler Matthias, Amati Matteo, Gregoratti Luca, Sirotina Anna P, Abakumov Artem M, Sánchez-Barriga Jaime, Yashina Lada V
Lomonosov Moscow State University, Leninskie Gory 1/3, 119991Moscow, Russia.
N.N. Semenov Federal Research Center for Chemical Physics, Kosygina Street 4, 119991Moscow, Russia.
ACS Nano. 2022 Dec 27;16(12):20831-20841. doi: 10.1021/acsnano.2c08217. Epub 2022 Nov 15.
Magnetic topological insulators (MTIs) have recently become a subject of poignant interest; among them, Z topological insulators with magnetic moment ordering caused by embedded magnetic atoms attract special attention. In such systems, the case of magnetic anisotropy perpendicular to the surface that holds a topologically nontrivial surface state is the most intriguing one. Such materials demonstrate the quantum anomalous Hall effect, which manifests itself as chiral edge conduction channels that can be manipulated by switching the polarization of magnetic domains. In the present paper, we uncover the atomic structure of the bulk and the surface of MnSbBiTe in conjunction with its electronic and magnetic properties; this material is characterized by naturally formed ferromagnetic layers inside the insulating matrix, where the Fermi level is tuned to the bulk band gap. We found that in such mixed crystals septuple layers (SLs) of Mn(Bi,Sb)Te form structures that feature three SLs, each of which is separated by two or three (Bi,Sb)Te quintuple layers (QLs); such a structure possesses ferromagnetic properties. The surface obtained by cleavage includes terraces with different terminations. Manganese atoms preferentially occupy the central positions in the SLs and in a very small proportion can appear in the QLs, as indirectly indicated by a reshaped Dirac cone.
磁性拓扑绝缘体（MTIs）近来成为了备受关注的课题；其中，由嵌入磁性原子引起磁矩有序排列的Z拓扑绝缘体格外引人注目。在这类体系中，具有拓扑非平庸表面态且垂直于表面的磁各向异性情形最为引人入胜。这类材料展现出量子反常霍尔效应，其表现为可通过切换磁畴极化来操控的手性边缘传导通道。在本文中，我们结合MnSbBiTe的电子和磁性性质揭示了其体相和表面的原子结构；这种材料的特征是在绝缘基体内部自然形成铁磁层，其中费米能级被调谐到体带隙。我们发现，在这类混合晶体中，Mn(Bi,Sb)Te的七层结构（SLs）形成了具有三个SLs的结构，每个SLs被两到三个（Bi,Sb）Te的五层结构（QLs）隔开；这样的结构具有铁磁性质。通过解理得到的表面包含具有不同终止情况的平台。锰原子优先占据SLs的中心位置，并且如重整化的狄拉克锥间接表明的那样，只有极小比例的锰原子会出现在QLs中。
