High-pressure synthesis of Dirac materials: layered van der Waals bonded BeN$_4$ polymorph

TL;DR

This paper reports the high-pressure synthesis of novel beryllium polynitrides, revealing a new 2D Dirac material with graphene-like electronic properties and layered van der Waals bonding, expanding the landscape of layered materials.

Contribution

It introduces a new class of 2D materials, beryllonitrene, with Dirac points and layered structure, synthesized via high-pressure chemistry and characterized by theoretical and experimental methods.

Findings

Synthesis of monoclinic and triclinic BeN4 at ~90 GPa.

Transformation into layered BeN4 with Dirac points.

Identification of a new 2D Dirac material, beryllonitrene.

Abstract

High pressure chemistry is known to inspire the creation of unexpected new classes of compounds with exceptional properties. Here we report the synthesis at ~90 GPa of novel beryllium polynitrides, monoclinic and triclinic BeN4. The triclinic phase, upon decompression to ambient conditions, transforms into a compound with atomic-thick BeN4 layers interconnected via weak van der Waals bonds consisting of polyacetylene-like nitrogen chains with conjugated {\pi}-systems and Be atoms in square-planar coordination. Theoretical calculations for a single BeN4 layer show that its electronic lattice is described by a slightly distorted honeycomb structure reminiscent of the graphene lattice and the presence of Dirac points in the electronic band structure at the Fermi level. The BeN4 layer, i.e. beryllonitrene, represents a qualitatively new class of 2D materials that can be built of a metal atom and polymeric nitrogen chains and host anisotropic Dirac fermions.