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

Abstract

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.

5 pages, 5 figures

References in corpus (6)

• Layer-dependent properties of SnS2 and SnSe2 novel two-dimensional materials
• A quantum phase transition from triangular to stripe charge order in NbSe${}_2$
• Molecular beam epitaxy growth and scanning tunneling microscopy study of TiSe${}_2$ ultrathin films
• Field-effect transistors of high-mobility few-layer SnSe${}_2$
• Superconductivity in Li-intercalated 1T-SnSe2 driven by electric-field gating
• Substrate-induced suppression of charge density wave in monolayer 1H-TaS2 on Au(111)