Peng Lang, Qiao Jingsi, Xian Jing-Jing, Pan Yuhao, Ji Wei, Zhang Wenhao, Fu Ying-Shuang
School of Physics and Wuhan National High Magnetic Field Center , Huazhong University of Science and Technology , Wuhan 430074 , China.
Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-Nano Devices, Department of Physics , Renmin University of China , Beijing 100872 , China.
ACS Nano. 2019 Feb 26;13(2):1885-1892. doi: 10.1021/acsnano.8b08051. Epub 2019 Jan 23.
Heterostructures of two-dimensional layered materials can be functionalized with exotic phenomena that are unpresented with each constituting component. The interface effect plays a key role in determining the electronic properties of the heterostructure, whose characterization requires a correlation with the morphology with atomic-scale precision. Here, we report an investigation on the electronic properties of few-layer Bi(110) films mediated by a NbSe substrate. By utilizing scanning tunneling microscopy and spectroscopy, we show a significant variation of the density of states at different Bi film thicknesses, resulting in an unusual superconducting proximity effect that deviates from the conventional monotonous decay behavior. Moreover, the electronic states of the Bi films are also prominently modulated by the Moiré pattern spatially. With first-principles calculations, we illuminate these findings as the results of covalent-like quasi-bonds formed at the Bi/NbSe interface, which profoundly alter the charge distributions in the Bi films. Our study indicates a viable way of modulating the electronic properties of ultrathin films by quasi-covalent interfacial couplings beyond conventional van der Waals interactions.
二维层状材料的异质结构可以通过奇异现象进行功能化，而这些奇异现象在每个组成部分中并不存在。界面效应在决定异质结构的电子性质方面起着关键作用，其表征需要与具有原子尺度精度的形态学相关联。在这里，我们报告了一项关于由NbSe衬底介导的少层Bi(110)薄膜电子性质的研究。通过利用扫描隧道显微镜和光谱学，我们展示了不同Bi薄膜厚度下态密度的显著变化，导致了一种不同于传统单调衰减行为的异常超导邻近效应。此外，Bi薄膜的电子态在空间上也受到莫尔条纹的显著调制。通过第一性原理计算，我们将这些发现解释为在Bi/NbSe界面形成的类共价准键的结果，这些准键深刻地改变了Bi薄膜中的电荷分布。我们的研究表明了一种通过超越传统范德华相互作用的准共价界面耦合来调制超薄薄膜电子性质的可行方法。
