论文标题
缺少铁磁cr $ _x $（bi $ _ {0.1} $ sb $ _ {0.9} $）$ _ {2-x} $ _3 $ _3 $
Absence of a Dirac gap in ferromagnetic Cr$_x$(Bi$_{0.1}$Sb$_{0.9}$)$_{2-x}$Te$_3$
论文作者
论文摘要
磁力破坏了预期在3D拓扑绝缘子中打开狄拉克间隙的时间逆向对称性，从而导致量子异常的效果。诱导铁磁状态的最常见方法是将磁性3 $ d $元素掺入大部分3D拓扑绝缘子中。在cr $ _ {0.15} $（bi $ _ {0.1} $ sb $ _ {0.9} $）$ _ {1.85} $ _ {1.85} $ te $ _3 $，量子异常效果最初在温度下发现的量子异常效应，比富特光电过渡的较大的dire circepiph，$ tircy the $ tircy the $ tircy gen，$ tircy the $ tirac $ the circation scanning the scanning the scanning the scanning the scanning the scanning the grap， $ \ sim20-100 $ mev。在磁性拓扑绝缘子中发现的量子异常效应（$ \ ll t_c $）的低温（$ \ ll t_c $）与较大的光谱dirac间隙（$ \ gg t_c $）之间的差异仍然令人困惑。在这里，我们使用角度分辨光发射光谱研究了Cr $ _ {0.15} $的原始和掺杂表面的表面电子结构（bi $ _ {0.1} $ _ {0.1} $ sb $ _ {0.9} $ _ {1.85} $ _ {1.85} $ _ {1.85} $ _3 $ _3 $ _3 $ _3 $。钾沉积后，原始样品的$ p $ - 型表面状态变成了$ n $ type，从而可以对Dirac Point进行光谱观察。我们发现了无间隙的表面状态，没有证据表明在隧道研究中报告了较大的狄拉克间隙。
Magnetism breaks the time reversal symmetry expected to open a Dirac gap in 3D topological insulators that consequently leads to quantum anomalous Hall effect. The most common approach of inducing ferromagnetic state is by doping magnetic 3$d$ elements into bulk of 3D topological insulators. In Cr$_{0.15}$(Bi$_{0.1}$Sb$_{0.9}$)$_{1.85}$Te$_3$, the material where the quantum anomalous Hall effect was initially discovered at temperatures much lower than the ferromagnetic transition, $T_C$, the scanning tunneling microscopy studies have reported a large Dirac gap $\sim20-100$ meV. The discrepancy between the low temperature of quantum anomalous Hall effect ($\ll T_C$) and large spectroscopic Dirac gaps ($\gg T_C$) found in magnetic topological insulators remains puzzling. Here, we used angle-resolved photoemission spectroscopy to study the surface electronic structure of pristine and potassium doped surface of Cr$_{0.15}$(Bi$_{0.1}$Sb$_{0.9}$)$_{1.85}$Te$_3$. Upon potassium deposition, the $p$-type surface state of pristine sample was turned into an $n$-type, allowing spectroscopic observation of Dirac point. We find a gapless surface state, with no evidence of a large Dirac gap reported in tunneling studies.
