We investigate electron transport through Hg Te ribbons embedded by strip-shape gate voltage through using a nonequilibrium Green function technique. The numerical calculations show that as the gate voltage is increased, an edgerelated state in the valence band structure of the system shifts upwards, then hangs inside the band gap and merges into the conduction band finally. It is interesting that as the gate voltage is increased continuously, another edge-related state in the valence band also shifts upwards in the small-k region and contacts the previous one to form a Dirac cone in the band structure. Meanwhile in this process, the conductance spectrum displays as multiple resonance peaks characterized by some strong antiresonance valleys in the band gap, then behaves as Fabry–P＇erot oscillations and finally develops into a nearly perfect quantum plateau with a value of 2e^2/h. These results give a physical picture to understand the formation process of the Dirac state driven by the gate voltage and provide a route to achieving particular quantum oscillations of the electronic transport in nanodevices.
The title compound [Cu（bbpy）（H2bptc）]n （bbpy = 4,4＇-dimethyl-2,2＇-bipyridine and H4bptc = 1,1＇-biphenyl-2,2？,3,3＇-tetracarboxylic acid） has been synthesized by hydrothermal reaction, and its structure was determined by X-ray diffraction and characterized by elemental analysis, IR spectrum and thermogravimetric analysis. The crystal is of triclinic, space group P1 with a = 11.2831（12）, b = 11.6718（13）, c = 11.7771（13）, α = 105.392（2）, β = 108.382（2）, γ = 112.397（2）o, CuC28H20N2O8, Mr = 576.00, V = 1222.4（2）3, Dc = 1.565 g/cm3, F（000） = 590, μ = 0.951 mm-1, S = 1.022 and Z = 2. The final refinement gave R = 0.0405 and wR = 0.1142 for 4270 observed reflections with I 2σ（I）. The title complex has a 1D [Cu（bbpy）（H2bptc）]n chain structure, in which the extensive hydrogen-bond interactions make the chain more stable. The neighboring parallel chains are further packed into a 2D layer structure via π···π stacking interaction between the pyridine rings of bbpy ligands. Moreover, the adjacent layers are interconnected by the C–H···π interactions to form a 3D metal-organic framework.
The title compound {[Cu（abpy）2]（H3bptc）·（H2O）}n, an ion-pair complex of [Cu（abpy）2]＋ with [（H3bptc）]- （abpy = 3,3＇-dimethyl-2,2＇-bipyridine and H4bptc = 1,1＇-biphenyl-2,2＇,3,3＇-tetracarboxylic acid）, has been synthesized by a hydrothermal reaction, and its structure was deter- mined by X-ray diffraction and characterized by elemental analysis and IR spectrum. The crystal is of triclinic, space group P1 with a = 8.4955（12）, b = 15.164（2）, c = 15.303（2）, α = 105.704（3）, β = 97.374（3）, γ = 96.764（3）o, CuC40H35N4O9, Mr = 779.26, V = 1857.9（4）3, Dc = 1.393 g/cm3, F（000） = 808, μ = 0.649 mm-1, S = 1.026 and Z = 2. The final R = 0.0493 and wR = 0.1034 for 4026 observed reflections with I 2σ（I）. The copper（I） coordination polymer demonstrates a 3-D sandwich-type structure containing 2-D double H3bptc-chain layers intercalated with the [Cu（abpy）2]＋ layers by extensive hydrogen bonding interactions.
