论文标题
来自原子薄的MNBI2TE4的第二次谐波产生4
Anomalous Second Harmonic Generation from Atomically Thin MnBi2Te4
论文作者
论文摘要
MNBI2TE4是一种范德华拓扑绝缘子，具有固有的内部内部铁磁交换和A型抗磁性磁磁相互层偶联。从理论上讲，它属于一类结构中心对称晶体，其分层的抗磁磁序破坏了偶数层数的反转对称性，使光学第二次谐波生成（SHG）成为晶体和磁性结构之间耦合的理想探针。在这里，我们对从大量到单层厚度的MNBI2TE4薄片进行磁场和温度依赖性SHG测量。我们发现来自MNBI2TE4的主要SHG信号与磁态和层数无关。我们建议表面SHG可能是观察到的强SHG的来源，其对称性与MNBI2TE4-VACUUM界面相匹配。我们的结果强调了考虑对范德华中心对称磁体中反转对称性对称性的表面贡献的重要性。
MnBi2Te4 is a van der Waals topological insulator with intrinsic intralayer ferromagnetic exchange and A-type antiferromagnetic interlayer coupling. Theoretically, it belongs to a class of structurally centrosymmetric crystals whose layered antiferromagnetic order breaks inversion symmetry for even layer numbers, making optical second harmonic generation (SHG) an ideal probe of the coupling between the crystal and magnetic structures. Here, we perform magnetic field and temperature-dependent SHG measurements on MnBi2Te4 flakes ranging from bulk to monolayer thickness. We find that the dominant SHG signal from MnBi2Te4 is unexpectedly unrelated to both magnetic state and layer number. We suggest that surface SHG is the likely source of the observed strong SHG, whose symmetry matches that of the MnBi2Te4-vacuum interface. Our results highlight the importance of considering the surface contribution to inversion symmetry-breaking in van der Waals centrosymmetric magnets.
