Momentum matching and band-alignment type in van der Waals heterostructures: Interfacial effects and materials screening

Momentum-matched type II van der Waals heterostructures (vdWHs) have been\ndesigned by assembling layered two-dimensional semiconductors (2DSs) with\nspecial band-structure combinations - that is, the valence band edge at the\nGamma point (the Brillouin-zone center) for one 2DS and the conduction band\nedge at the Gamma point for the other [Ubrig et al., Nat. Mater. 19, 299\n(2020)]. However, the band offset sizes, band-alignment types, and whether\nmomentum matched or not, all are affected by the interfacial effects between\nthe component 2DSs, such as the quasichemical-bonding (QB) interaction between\nlayers and the electrical dipole moment formed around the vdW interface. Here,\nbased on density-functional theory calculations, first we probe the interfacial\neffects (including different QBs for valence and conduction bands, interface\ndipole, and, the synergistic effects of these two aspects) on band-edge\nevolution in energy and valley (location in the Brillouin zone) and the\nresulting changes in band alignment and momentum matching for a typical vdWH of\nmonolayer InSe and bilayer WS2, in which the band edges of subsystems satisfy\nthe special band-structure combination for a momentum-matched type II vdWH.\nThen, based on the conclusions of the studied interfacial effects, we propose a\npractical screening method for robust momentum-matched type II vdWHs. This\npractical screening method can also be applied to other band alignment types.\nOur current study opens a way for practical screening and designing of vdWHs\nwith robust momentum-matching and band alignment type.\n