| Graphyne has amazing electronic properties.Although the electronic,optical and mechanical properties of graphyne and graphyne nanoribbon have been extensively stud-ied,the electronic transport properties have not been clearly studied.The first part of this thesis introduces the lattice structure and basic feature of gra-phyne and energy band structure of graphyne nanoribbons.The second part introduces the theoretical model and research method.In the third part,the band structure and electron transport property of ?-graphyne nanoribbons under electric field and Coulomb repulsion are studied by the tight-binding method.We find that the energy gap of zigzag-edged ?-graphyne nanoribbons increases linearly with the Coulomb repulsion.The band gap of the armchair-edged ?-graphyne nanoribbons and the zigzag-edged ?-graphyne nanoribbons oscillate with electric field,a metal insulator phase transition appears.In the presence of electric field and Coulomb re-pulsion,a half-metallicity and a half-metal insulator phase transition occur in ?-graphyne nanoribbons.In the fourth part,we investigate the energy gap and half-metallicity of the zigzag-edged,?-graphyne nanoribbons via a tight-binding approach.In the presence of Coulomb repulsion and proper transverse electric field strengths,the nanoribbons are forced into half-metallicity by the electric field.A phase transition from half-metal to insulator is realized by changing the electric field or Coulomb potential.Both the electric field and Coulomb repulsion can open direct band gaps,resulting in a metal-insulator phase tran-sition.The band gaps oscillate with the electric field,contrary to linear change with the Coulomb potential.In summary,we mainly study energy gap,half-metallicity and phase transition of?-graphyne nanoribbons and ?-graphyne nanoribbons in the presence Coulomb repulsion and transverse electric field.We expect that these results will have a certain reference value in the field of spintronics. |
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