Odd-Even Layer-Number Effect and Layer-Dependent Magnetic Phase Diagrams in MnBi2Te4
Odd-Even Layer-Number Effect and Layer-Dependent Magnetic Phase Diagrams in MnBi2Te4
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MnBi2Te4 中的奇偶层数效应和层相关磁相图
DOI：
10.1103/physrevx.11.011003
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发表时间：
2021-01-06
影响因子：
12.5
通讯作者：
Ye, Yu
中科院分区：
文献类型：
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作者：
Yang, Shiqi;Xu, Xiaolong;Ye, Yu
最近报道，MnBi 2 Te 4具有非平凡的拓扑性质和磁序，是一种本征磁性拓扑绝缘体，有望探索量子异常霍尔效应等奇异量子现象。然而，MnBi 2 Te 4的层相关磁性，这是进一步探索该系统中相关量子现象的基础和关键，仍然难以捉摸。在这里，通过使用极性反射磁性圆二色光谱，我们表明，少层MnBi 2 Te 4表现出明显的奇偶层数效应，即，磁滞回线（μ H-0（c）处）和自旋翻转跃迁（μ H-0（1）处）的双极性振荡，涉及塞曼能和磁各向异性能。值得注意的是，在偶数层七层MnBi（2）Te（4）4中观察到了一个异常的磁滞回线，这可能归因于厚度无关的表面相关磁化。一个线性链模型被施加到阐明这种奇数-偶数层的自旋翻转场的影响，并确定在受到外部磁场时的磁状态的演变。平均场方法进一步使我们能够充分映射MnBi 2 Te 4薄片的磁相图中的磁场，层数，特别是温度的参数空间。通过利用不寻常的层相关的磁性，我们的工作铺平了道路，为进一步研究MnBi 2 Te 4的量子现象。
Recently reported with nontrivial topological properties and magnetic orders, MnBi2Te4 is an intrinsic, magnetic topological insulator which holds promise for exploring exotic quantum phenomena such as the quantum anomalous Hall effect. However, the layer-dependent magnetism of MnBi2Te4, which is fundamental and crucial for further exploration of related quantum phenomena in this system, remains elusive. Here, by using polar reflective magnetic circular dichroism spectroscopy, we show that few-layered MnBi2Te4 exhibits an evident odd-even layer-number effect, i.e., the oscillations of the coercivity of the hysteresis loop (at mu H-0(c)) and the spin-flop transition (at mu H-0(1)), concerning the Zeeman energy and magnetic anisotropy energy. Noticeably, an anomalous magnetic hysteresis loop is observed in the evennumber septuple-layered MnBi(2)Te(4)4, which might be attributed to the thickness-independent surfacerelated magnetization. A linear-chain model is applied to elucidate this odd-even layer-number effect of the spin-flop field and to determine the evolution of the magnetic states when subjected to an external magnetic field. A mean-field method further allows us to fully map the MnBi2Te4 flake's magnetic phase diagrams in the parameter space of the magnetic field, layer number, and, especially, temperature. By harnessing the unusual layer-dependent magnetic properties, our work paves the way for further study of quantum phenomena of MnBi2Te4.