论文标题
关于缺陷在MNBI $ _ {2-x} $ sb $ _x $ te $ _4 $的电子结构中的作用
On the Role of Defects in the Electronic Structure of MnBi$_{2-x}$Sb$_x$Te$_4$
论文作者
论文摘要
元素替换是拓扑绝缘子中Fermi级调整的一种经过验证的方法，这是设备应用所需的。通过静态和时间解决的光发射，我们表明，在MNBI $ _2 $ TE $ _4 $中，BI的元素替代SB确实使Fermi水平调整为散装频段间隙，从而使材料电荷在35 \％\％SB浓度下进行中性。我们第一次能够直接在此掺杂水平上直接探测激发的状态带结构，它们的动力学表明，在费米水平上的衰减通道受到严格限制。但是，元素取代扩大了表面状态间隙，我们将其归因于SB替代导致的反site缺陷的增加。该假设得到了包括缺陷的DFT计算的支持，这些计算表明拓扑表面状态对它们的包容性具有敏感性。我们的结果强调了如果MNBI $ _ {2-x} $ sb $ _x $ _x $ te $ _4 $用于设备应用程序，则需要进行缺陷控制。
Elemental substitution is a proven method of Fermi level tuning in topological insulators, which is needed for device applications. Through static and time resolved photoemission, we show that in MnBi$_2$Te$_4$, elemental substitution of Bi with Sb indeed tunes the Fermi level towards the bulk band gap, making the material charge neutral at 35\% Sb concentration. For the first time, we are able to directly probe the excited state band structure at this doping level, and their dynamics, which show that the decay channels at the Fermi level are severely restricted. However, elemental substitution widens the surface state gap, which we attribute to the increase in antisite defects resulting from Sb substitution. This hypothesis is supported by DFT calculations that include defects, which show a sensitivity of the topological surface state to their inclusion. Our results emphasize the need for defect control if MnBi$_{2-x}$Sb$_x$Te$_4$ is to be used for device applications.
