Atomic vacancies and nanopores act as local scattering centers and modify the transport properties of charge carriers in phosphorene nanoribbons (PNRs). We investigate the influence of such atomic defects on the electronic transport of multi-terminal PNR. We use the non-equilibrium Green's function approach within the tight-binding framework to calculate the transmission coefficient and the conductance. Terminals induce band mixing resulting in oscillations in the conductance. In the presence of atomic vacancies and nanopores the conductance between non-axial terminals exhibit constructive scattering, which is in contrast to mono-axial two-terminal systems where the conductance exhibits destructive scattering. This can be understood from the spatial local density of states of the transport modes in the system. Our results provide fundamental insights into the electronic transport in PNR-based multi-terminal systems and into the ability of atomic defects and nanopores through tuning the transport properties.
Electron transport in a graphene quantum well can be analogous to photon transmission in an optical fiber. In this work, we present a detailed theoretical analysis to study the transport characteristics of graphene waveguides under the influence of different edge orientations. Non-equilibrium Green's function approach in combination with tight-binding Hamiltonian has been utilized to investigate the conductance properties of straight armchair and zigzag oriented graphene waveguides. Conductance plateaus at integer steps of 4e 2 /h have been observed in both orientations while the zigzag oriented waveguides present a wider first quantized plateau compared to that in the armchair oriented ones. Using various geometric and physical parameters, including side-barrier and waveguide width, and the metallic properties of terminals, we investigate the conductance profile of waveguides. In addition to the observation of valley-symmetry in both edge orientations, this article explores the critical influence of drain contacts on waveguide conductance. Furthermore, we extended our transport study to three different highly bent waveguide configurations, such as Ushape, L-shape and split-shape waveguides, in order to explore their applications in graphene-based ballistic integrated circuit devices. In the end, we also calculated the conductance of larger graphene waveguides using the scalable tight-binding model, in order to compare the results obtained from the original model. arXiv:1901.00292v2 [cond-mat.mes-hall]
Behavior of different planar multilayer periodic structures due to plane wave excitation has been studied using the transfer matrix method. Multilayer structure is composed of odd number of slabs and the layers at odd locations have same characteristics and layers at even locations have same characteristics. For each structure, layers at odd locations are of chiral nihility metamaterial whereas three different cases are considered for layers at even locations, i.e., dielectric, chiral and chiral nihility. Effects of polarization rotation due to the optical activity of material's chirality is studied with respect angle of incidence and frequency in THz region. Chiral nihility adds property of transparency to the structure for normal incidence. Chiral nihility-chiral nihility structure for normal incidence yields transparency whereas same structure for oblique incidence yields total rejection at higher frequencies. .
N.A. Shah et al. / Effects on reflected and transmitted powers of planar stratified structurescomposed of nihility metamaterial [5]. Later, Tretyakov et al. extended the concept of nihility for the isotropic chiral metamaterials [6]. Chiral nihility (CN) is a special case of chiral metamaterial for which real part of permittivity and permeability are simultaneously zero at certain frequency, i.e., −→ 0 and μ −→ 0. The constitutive relations for CN metamaterials are [6][7][8],
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