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arXiv 2102.07913cond-mat.mtrl-scicond-mat.supr-con
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单层和双层SnSe $_2$中的电荷密度波和费米能级钉扎

Charge density waves and Fermi level pinning in monolayer and bilayer SnSe$_2$

Shu-Ze Wang, Yi-Min Zhang, Jia-Qi Fan, Ming-Qiang Ren, Can-Li Song, Xu-Cun Ma, Qi-Kun Xue

摘要:

具有降低维度的材料通常表现出不同于其本体对应物的特殊性质。在这里,我们报告了一个相称的2 $\times$ 2电荷密度波(CDW)的出现在单层和双层SnSe $_2$薄膜的扫描隧道显微镜。CDW相位的可视化空间调制在费米能级附近变得突出,费米能级被钉扎在SnSe $_2$的半导体带隙内。我们发现,CDW和费米能级钉扎密切相关的带弯曲和虚拟诱导间隙状态在半导体异质界面。通过界面工程,建立了SnSe $_2$的电子密度依赖相图。费米面之间的对称性不等电子口袋嵌套揭示驱动CDW的形成,并提供一个替代的CDW机制,可能会在其他化合物。

英文摘要:

Materials with reduced dimensionality often exhibit exceptional properties that are different from their bulk counterparts. Here we report the emergence of a commensurate 2 $\times$ 2 charge density wave (CDW) in monolayer and bilayer SnSe$_2$ films by scanning tunneling microscope. The visualized spatial modulation of CDW phase becomes prominent near the Fermi level, which is pinned inside the semiconductor band gap of SnSe$_2$. We show that both CDW and Fermi level pinning are intimately correlated with band bending and virtual induced gap states at the semiconductor heterointerface. Through interface engineering, the electron-density-dependent phase diagram is established in SnSe$_2$. Fermi surface nesting between symmetry inequivalent electron pockets is revealed to drive the CDW formation and to provide an alternative CDW mechanism that might work in other compounds.

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