Understanding the interlayer coupling in 1 T / 1 H − NbSe 2 heterobilayers

Abstract

The properties of 2D materials are strongly influenced by their substrate, leading to a variety of proximity effects like screening, charge transfer, and hybridization. Surprisingly, there is a dearth of theoretical studies on these effects. Particularly, previous theoretical research on the star of David (SOD) structure in 1⁢−NbSe2 has focused on single-layer configurations or stacking with the same 1⁢ phase without any real substrate. Here, we depart from these approaches and explore how these proximity effects shape the electronic and magnetic properties of the 1⁢−NbSe2 phase when it is grown on the metallic 1⁢−NbSe2 substrate. Using density functional calculations, we establish a common framework to define the key characteristics of both free-standing 1⁢−NbSe2 and 1⁢−NbSe2. We then identify the optimal stacking arrangement for these two layers, revealing a transfer from the 1⁢ to the 1⁢ phase and a reorganization of charge within each layer. Our findings indicate that the magnetic moment of the SOD structure is still robust; however, it is diminished due to a reduction in the on-site Coulomb interaction of the Hubbard bands. Additionally, the interlayer coupling induces metallicity in the 1⁢ phase and increases the decoupling of the lower Hubbard band from the valence band.