Graphene-like conjugated pi-bond system in Pb1-xSnxSe

Abstract

Following the identification of the pi bond in graphene, in this work, a pi bond constructed through side-to-side overlap of half-filled 6pz orbitals was observed in a non-carbon crystal of Pb1-xSnxSe (x=0.34) (PSS), a prototype topological crystalline insulator (TCI) and thermoelectric material with a high figure-of-merit (ZT). PSS compounds with a rock-salt type cubic crystal structure was found to consist of sigma bond connected covalent chains of Pb(Sn)-Se with an additional pi bond that is shared as a conjugated system among the four nearest neighbor Pb pairs in square symmetry within all (001) monoatomic layers per cubic unit cell. The pi bond formed with half-filled 6pz orbitals between Pb atoms is consistent with the calculated results from quantum chemistry. The presence of pi bonds was identified and verified with electron energy-loss spectroscopy (EELS) through plasmonic excitations and electron density (ED) mapping via an inverse Fourier transform of X-ray diffraction.

arXiv comment5 pages, 4 figures, to be published in Appl Phys. Lett

References in corpus (8)

• The electronic properties of graphene
• Topological Insulators
• Topological Crystalline Insulators
• Topological crystalline insulator states in Pb(1-x)Sn(x)Se
• A topological crystalline insulator (TCI) phase via topological phase transition and crystalline mirror symmetry
• Observation of Dirac node formation and mass acquisition in a topological crystalline insulator
• Topological insulators and thermoelectric materials
• Plasmons dispersion and nonvertical interband transitions in single-crystal Bi2Se3 investigated by electron energy loss spectroscopy