Unique Schrödinger semimetal state in ternary Be2P3N honeycomb lattice

Abstract

Two-dimensional (2D) materials with zero band gaps are of great significance in fundamental science and potential applications but are rather scarce. Here we report a novel 2D semimetal, a ternary beryllium–phosphorus–nitrogen Be₂P₃N honeycomb-lattice monolayer by first-principles calculations. This graphene-like Be₂P₃N monolayer is composed of Be and N tricoordinated with P₃ and exhibits excellent dynamic and thermal stabilities. Unlike the semimetal graphene with linear Dirac-cone energy-momentum dispersion, the Be₂P₃N monolayer is intrinsically gapless with parabolic E^±(k) ∼ ±k² band dispersion (the ± sign corresponds to the conduction and valence bands) in the low-energy vicinity, and features a peculiar “Schrödinger paraboloid”. The ±k² band state mainly originates from P-p_z electrons and has high stability against large external strains. This finding opens a new branch of semimetal nanomaterials research.