论文标题
关于在扫描隧道显微镜光谱中缺乏旋转轨道间隙的奥秘
On the mystery of the absence of a spin-orbit gap in scanning tunneling microscopy spectra of germanene
论文作者
论文摘要
德国石墨烯类似物的德国烯与其碳对应物共享许多物业。两种材料都是二维材料，可容纳狄拉克·费米子。但是，这两种材料之间也存在一些重要差异：（1）石墨烯具有平面蜂窝状晶格，而德国烯的蜂窝晶格则是弯曲的，（2）预计德国烯的旋转轨道间隙预计将比Graphene中的Spin-Orbit Gap（24 Mev for Germanene versene versus 20 $ 20 $ e evene）大约三个比例的尺度。令人惊讶的是，在不同底物上合成的德国层上记录的扫描隧道光谱没有显示出在德国烯中存在旋转轨道间隙的任何迹象。迄今为止，在扫描的德国扫描隧道光谱中缺乏这种自旋轨道差距的确切起源仍然是一个谜。在这项工作中，我们表明，旋转轨道的缺失可以通过Germanene的出色功能仅为3.8 em。德国烯与扫描隧道显微镜尖端之间的工作功能差异（最常用的STM尖端的工作函数在4.5至5.5 eV范围内）会导致隧道连接处的电场。该电场导致对自旋轨道间隙尺寸的强烈抑制。
Germanene, the germanium analogue of graphene, shares many properties with its carbon counterpart. Both materials are two-dimensional materials that host Dirac fermions. There are, however, also a few important differences between these two materials: (1) graphene has a planar honeycomb lattice, whereas germanene's honeycomb lattice is buckled and (2) the spin-orbit gap in germanene is predicted to be about three orders of magnitude larger than the spin-orbit gap in graphene (24 meV for germanene versus 20 $μ$eV for graphene). Surprisingly, scanning tunneling spectra recorded on germanene layers synthesized on different substrates do not show any sign of the presence of a spin-orbit gap in germanene. To date the exact origin of the absence of this spin-orbit gap in the scanning tunneling spectra of germanene has remained a mystery. In this work we show that the absence of the spin-orbit can be explained by germanene's exceptionally low work function of only 3.8 eV. The difference in work function between germanene and the scanning tunneling microscopy tip (the work functions of most commonly used STM tips are in the range of 4.5 to 5.5 eV) gives rise to an electric field in the tunnel junction. This electric field results in a strong suppression of the size of the spin-orbit gap.
