Two-dimensional Dirac fermions on oxidized black phosphorus

• Published in: Physical chemistry chemical physics : PCCP 2019-11, Vol.21 (43), p.2426-24211
• Main Authors: Kang, Seoung-Hun, Park, Jejune, Woo, Sungjong, Kwon, Young-Kyun
• Format: Article
• Language: English
• Subjects: Density functional theory; Electronic structure; Fermions; Free energy; Heat of formation; Infrared spectra; Lattice vibration; Mathematical analysis; Oxidation; Phosphorene; Phosphorus; Symmetry; Topology
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c9cp04372a

We explore the oxidation of a single layer of black phosphorus using ab initio density functional theory calculations. We search for the equilibrium structures of phosphorene oxides, PO x with various oxygen concentrations x (0 ≤ x ≤ 1). By evaluating the formation energies with diverse configurations and their vibrational properties for each of various x values, we identify a series of stable oxidized structures with x and confirm that the oxidation occurs naturally. We also find that oxidation makes some modes from the P-O bonds and P-P bonds IR-active implying that the infrared spectra can be used to determine the degree of oxidation of phosphorene. Our electronic structure calculations reveal that the fully oxidized phosphorene (PO) has a direct band gap of 0.83 eV similar to the pristine phosphorene. Intriguingly, the PO possesses two nonsymmorphic symmetries with the inversion symmetry broken, guaranteeing symmetry-protected band structures including the band degeneracy and four-fold degenerate Dirac points. Our results provide an important guide in the search for the rare example of a Dirac semimetal with a higher level of degeneracy, giving significant insight into the relations between the symmetry of the lattice and band topology of electrons. Using ab initio density functional theory calculations, we find four-fold degenerate Dirac points protected by two nonsymmorphic symmetries in phosphorene oxide with the inversion symmetry broken.