Large potential steps at weakly interacting metal-insulator interfaces

TL;DR

This paper investigates the origin of large potential steps at weakly interacting metal-insulator interfaces, revealing that exchange repulsion primarily causes these steps, with implications for understanding interface electronic properties.

Contribution

The study demonstrates that exchange repulsion, rather than interface bonding, mainly causes potential steps at weakly interacting interfaces, supported by first-principles calculations and a simple theoretical model.

Findings

Potential steps >1 eV occur at weakly interacting interfaces.

Exchange repulsion is the main contributor to potential steps.

Chemical bonding reduces the potential step in strong interactions.

Abstract

Potential steps exceeding 1 eV are regularly formed at metal|insulator interfaces, even when the interaction between the materials at the interface is weak physisorption. From first-principles calculations on metal|h-BN interfaces we show that these potential steps are only indirectly sensitive to the interface bonding through the dependence of the binding energy curves on the van der Waals interaction. Exchange repulsion forms the main contribution to the interface potential step in the weakly interacting regime, which we show with a simple model based upon a symmetrized product of metal and h-BN wave functions. In the strongly interacting regime, the interface potential step is reduced by chemical bonding.