Stacking-sequence-independent band structure and shear exfoliation of two-dimensional electride materials

TL;DR

This study reveals that the band structure of 2D Ca$_2$N electride remains nearly unchanged despite variations in stacking sequence and lateral shifts, due to complete electronic screening.

Contribution

It demonstrates the invariance of 2D electride band structures against stacking variations, enabling shear exfoliation and potential thermally stable electronic applications.

Findings

Band structure is insensitive to stacking sequence.

Weak interlayer interactions facilitate shear exfoliation.

Electronic properties are geometry-insensitive in 2D electride.

Abstract

The electronic band structure of crystals is generally influenced by the periodic arrangement of their constituent atoms. Specifically, the emerging two-dimensional (2D) layered structures have shown different band structures with respect to their stacking configurations. Here, based on first-principles density-functional theory calculations, we demonstrate that the band structure of the recently synthesized 2D Ca$_2$N electride changes little for the stacking sequence as well as the lateral interlayer shift. This intriguing invariance of band structure with respect to geometrical variations can be attributed to a complete screening of [Ca$_2$N]$^{+}$ cationic layers by anionic excess electrons delocalized between the cationic layers. The resulting weak interactions between 2D dressed cationic layers give rise to not only a shallow potential barrier for bilayer sliding but also an electron-doping facilitated shear exfoliation. Our findings open a route for exploration of the peculiar geometry-insensitive electronic properties in 2D electride materials, which will be useful for future thermally stable electronic applications.