Discovery of a new Dirac material, layered van der Waals bonded BeN4 polymorph

In collaboration between theory, visualization and experiment we predicted and confirmed experimentally a possibility to synthesize new layered compound with atomic-thick BeN4 layers interconnected via weak van der Waals bonds consisting of polyacetylene-like nitrogen chains with conjugated π-systems and Be atoms in square-planar coordination. Theoretical calculations for a single BeN4 layer showed that its electronic lattice could be 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. The results were highlighted as Editors’ Suggestion by the Physical Review Letters.

Figure 1. Crystal structure and charge density of tr-BeN4 at ambient pressure (left panel). Topological data analysis of the charge density carried out within our SeRC supported project in collaboration between theoretical physics and visualization groups confirmed a formation of van der Waals bonded material with stronger interaction within layers and weaker interaction between layers. A single BeN4 layer hosts Dirac points in the electronic band structure at the Fermi level (right panel).

Reference: High-pressure synthesis of Dirac materials: layered van der Waals bonded BeN4 polymorph M. Bykov, T. Fedotenko, S. Chariton, D. Laniel, K. Glazyrin, M. Hanfland, J. S. Smith, V. B. Prakapenka, M. F. Mahmood, A. F. Goncharov, A. V. Ponomareva, F. Tasnádi, A. I. Abrikosov, T. Bin Masood, I. Hotz, A. N. Rudenko, M. I. Katsnelson, N. Dubrovinskaia, L. Dubrovinsky, I. A. Abrikosov, Phys. Rev. Lett. 126, 175501 (2021);