High-Pressure Synthesis of Dirac Materials: Layered van der Waals Bonded BeN4 Polymorph

High-pressure chemistry is known to inspire the creation of unexpected new classes of compounds with exceptional properties. Here, we employ the laser-heated diamond anvil cell technique for synthesis of a Dirac material BeN4. A triclinic phase of beryllium tetranitride tr-BeN4 was synthesized from elements at similar to 85 GPa. Upon decompression to ambient conditions, it transforms into a compound with atomic-thick BeN4 layers interconnected via weak van der Waals bonds and 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.
Funding Agencies|Army Research Office; Deutsche Forschungsgemeinschaft (DFG)German Research Foundation (DFG) [DU 954-11/1, DU 393-9/2, DU 393-13/1]; Federal Ministry of Education and Research, Germany (BMBF)Federal Ministry of Education & Research (BMBF) [05K19WC1]; Alexander von Humboldt FoundationAlexander von Humboldt Foundation; Russian Science FoundationRussian Science Foundation (RSF) [18-12-00492]; Ministry of Science and Higher Education of the Russian Federation of Increase Competitiveness Program of NUST MISIS [K2-2020-026, 211]; Knut and Alice Wallenberg Foundation (Wallenberg Scholar Grant) [KAW-2018.0194]; Swedish Government Strategic Research Areas in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; SeRCAgency for Science Technology & Research (ASTAR); Swedish Research Council (VR)Swedish Research Council [2019-05600]; Vinnova VINN Excellence Center Functional Nanoscale Materials (FunMat-2) [2016-05156]; Swedish Research CouncilSwedish Research CouncilEuropean Commission [2016-07213]; JTC-FLAGERA Project GRANSPORT; National Science Foundation-Earth SciencesNational Science Foundation (NSF) [EAR-1634415]; Department of Energy-GeosciencesUnited States Department of Energy (DOE) [DE-FG0294ER14466]; DOENNSAs Office of Experimental Sciences; DOE Office of ScienceUnited States Department of Energy (DOE) [DE-AC02-06CH11357]; [W911NF-19-2-0172]