Single molecule DNA sequencing via transverse electronic transport using a graphene nanopore: A tight-binding approach

We report a tight-binding model study of two-terminal graphene nanopore based device, for sequential determination of DNA bases. Using Greens function approach we calculate conductance spectra, I-V response and also the changes in local density of states (LDOS) profile as four different nucleobases inserted one by one into the pore embedded in the zigzag graphene nanoribbon (ZGNR). We find distinct features in LDOS profile for different nucleotides and the same is also present in conductance and I-V response. We propose the actual working principle of the device, by setting the bias across the pore to a fixed voltage (this voltage gives maximum discrimination between characteristic current of the four nucleotides) and translocating the ss-DNA through the nanopore using a transverse electric field while recording the characteristic current of the nucleotides. Not only the typical current output is much larger than previous results, but the seaparation between them for different bases are also definite. Our investigation provides high accuracy and significant amount of distinction between different nucleotides.Comment: 6 pages, 5 figure

Ground state phase diagram and magnetoconductance of a one-dimensional Hubbard superlattice at half-filling

We have studied a one dimensional Hubbard superlattice with different Coulomb correlations at alternating sites for a half-filled band. Mean field calculations based on the Hartree-Fock approximation together with a real space renormalization group technique were used to study the ground state of the system. The phase diagrams obtained in these approaches agree with each other from the weak to the intermediate coupling regime. The mean field results show very quick convergence with system size. The renormalization group results indicate a spatial modulation of local moments that was identified in some previous work. Also we have studied the magnetoconductance of such superlattices which reveals several interesting points.Comment: 10 pages, 13 figures. to be published in Phys. Rev. B, vol. 75, Issue 23 (tentative

Integer quantum Hall effect in a square lattice revisited

We investigate the phenomenon of integer quantum Hall effect in a square lattice, subjected to a perpendicular magnetic field, through Landauer-B\"uttiker formalism within the tight-binding framework. The oscillating nature of longitudinal resistance and near complete suppression of momentum relaxation processes are examined by studying the flow of charge current using Landauer-Keldysh prescription. Our analysis for the lattice model corroborates the finding obtained in the continuum model and provides a simple physical understanding.Comment: 5 pages, 5 figure

Effect of Dephasing on Electron Transport in a Molecular Wire: Green's Function Approach

The effect of dephasing on electron transport through a benzene molecule is carefully examined using a phenomenological model introduced by B\"{u}ttiker. Within a tight-binding framework all the calculations are performed based on the Green's function formalism. We investigate the influence of dephasing on transmission probability and current-voltage characteristics for three different configurations ({\em ortho}, {\em meta} and {\em para}) of the molecular system depending on the locations of two contacting leads. The presence of dephasing provides a significant change in the spectral properties of the molecule and exhibits several interesting patterns that have so far remain unexplored.Comment: 8 pages, 10 figure