3 research outputs found
Shot Noise Probing of Magnetic Ordering in Zigzag Graphene Nanoribbons
The nonequilibrium time-dependent fluctuations of charge current have
recently emerged as a sensitive experimental tool to probe ballistic transport
through evanescent wave functions introduced into clean wide and short graphene
strips by the attached metallic electrodes. We demonstrate that such
"pseudo-diffusive" shot noise can be substantially modified in zigzag graphene
nanoribbon (ZGNR) due to the topology of its edges responsible for localized
states that facilitate ferromagnetic ordering along the edge when Coulomb
interaction is taken into account. Thus, the shot noise enhancement of
unpolarized, and even more sensitively of spin-polarized, charge currents
injected into ZGNR will act as an all-electrical and edge-sensitive probe of
such low-dimensional magnetism.Comment: 5 pages, 3 color figures; references update
Electron density and transport in top-gated graphene nanoribbon devices: First-principles Green function algorithms for systems containing large number of atoms
The recent fabrication of graphene nanoribbon (GNR) field-effect transistors
poses a challenge for first-principles modeling of carbon nanoelectronics due
to many thousand atoms present in the device. The state of the art quantum
transport algorithms, based on the nonequilibrium Green function formalism
combined with the density functional theory (NEGF-DFT), were originally
developed to calculate self-consistent electron density in equilibrium and at
finite bias voltage (as a prerequisite to obtain conductance or current-voltage
characteristics, respectively) for small molecules attached to metallic
electrodes where only a few hundred atoms are typically simulated. Here we
introduce combination of two numerically efficient algorithms which make it
possible to extend the NEGF-DFT framework to device simulations involving large
number of atoms. We illustrate fusion of these two algorithms into the
NEGF-DFT-type code by computing charge transfer, charge redistribution and
conductance in zigzag-GNR/variable-width-armchair-GNR/zigzag-GNR two-terminal
device covered with a gate electrode made of graphene layer as well. The total
number of carbon and edge-passivating hydrogen atoms within the simulated
central region of this device is ~7000. Our self-consistent modeling of the
gate voltage effect suggests that rather large gate voltage might be required
to shift the band gap of the proposed AGNR interconnect and switch the
transport from insulating into the regime of a single open conducting channel.Comment: 19 pages, 8 PDF figures, PDFLaTe