Abinitio calculations on the electronic properties of an encapsulated pair of polyynes inside a semiconductor zigzag carbon nanotube K Chaibedderraa, H Khalfoun, H Bouhani Benziane, T Hadji Physica Scripta, 2026 We present a first-principles investigation of the structural and electronic properties of linear carbon chains encapsulated inside a zigzag carbon nanotube (10,0). Using density functional theory as implemented in the SIESTA code, we investigate both single- and double-chain configurations under periodic boundary conditions. Non-covalent functionalization is taken into account through van der Waals interactions.For the single-chain system, confinement inside the nanotube leads to a complete suppression of the bond-length alternation, driving a transition from a polyyne to a cumulene-like structure and inducing metallic behavior. In contrast, the encapsulation of two interacting chains results in an anti-parallel stacking configuration that preserves a finite bond-length alternation (~0.027Å) and opens a narrow indirect band gap of approximately 80 meV. Furthermore, the application of longitudinal mechanical compression progressively reduces the bond-length alternation and triggers a semiconductor-to-metal transition at strain values exceeding −2%. These results demonstrate that interchain coupling and external strain provide effective mechanisms for tuning the electronic properties of one-dimensional carbon-based hybrid nanostructures.
Transport regimes in nitrogen-doped carbon nanotubes: Perfect order, semi-random, and random disorder cases Hafid Khalfoun, Aurélien Lherbier, Philippe Lambin, Luc Henrard, Jean-Christophe Charlier Physical Review B Condensed Matter and Materials Physics, 2015 The electronic structure and the transport properties of nitrogen-doped carbon nanotubes are investigated using a tight-binding model and a real-space Kubo-Greenwood approach, respectively. The transport regimes of various axial and helical doping configurations, from perfectly periodic to fully random disordered cases, are examined through the time dependence of the diffusivity. By varying the degree of disorder, a rich set of transient regimes is predicted going from persisting quasiballistic to momentarily localized regimes. A spectacular long-time ballistic regime is also observed for a specific semi-random disorder doping configuration owing to symmetry effects.
Long-range resonant effects on electronic transport of nitrogen-doped carbon nanotubes Hafid Khalfoun, Philippe Lambin, Luc Henrard Physical Review B Condensed Matter and Materials Physics, 2014 (Received 30 August 2013; revised manuscript received 1 October 2013; published 13 January 2014)The electronic transport properties of ordered and disordered nitrogen-doped metallic carbon nanotubes withlong-rangecorrelationarestudiednumericallywithatight-bindingmodel.Dopingwithbothtranslational(axial)and screw symmetry are considered. In periodic defective systems, when axial doping is considered, two classesof electronic transport responses are obtained. One quantum conductance plateau settles down around the defectenergy only when the period of the structure is a multiple of the Fermi wavelength 3
B and N codoping effect on electronic transport in carbon nanotubes Hafid Khalfoun, Patrick Hermet, Luc Henrard, Sylvain Latil Physical Review B Condensed Matter and Materials Physics, 2010 We present here an analysis of the electronic-quantum properties of B and N codoping of carbon nanotubes. We show that BN pairs are transparent for conduction electrons. Localized transport phenomena, observed for isolated B or N doping, are recovered when B and N atoms are far apart. We also analyze the effect of BN nanodomains on the quantum conductance and demonstrate the drastic effect of the B-N ``parity'' and of the shape of the domain. Our simulations have been performed at the density-functional-theory level and within Green's function Landauer approach. However, we show that a one-parameter (on-site energy) model could catch the main features of the transport properties of BN codoping effect on electronic transport
Nature of the enhanced resonant modes in one-dimensional photonic random dimer systems H Khalfoun, M Bouamoud, S Bentata, L Henrard, C Vandenbem Journal of Optics A Pure and Applied Optics, 2009 The propagation of light in a one-dimensional multilayer stack is examined for a disordered system with short range correlation. As known in the random dimer model, pairing the defect elements at random breaks down the Anderson localization and opens a frequency window of extended propagating modes around the predicted conventional dimer resonance. By dealing with host and defect layers with identical phase thicknesses at both host and defect principal standing resonances, we demonstrate the existence of a new ballistic-like regime at an additional standing commuting resonance. Moreover, by suitably tuning the host standing and conventional defect dimer resonances relative to each other, the transmission responses are both turned into a ballistic transmission regime. By scaling the transmission coefficient over the system length within the resonance window, we analyse the nature of the propagating modes, i.e. ballistic or diffusive. Beyond the resonance, quantitative views on the different transmission regimes and their related phase transitions are examined, pointing out the possibility of designing attractive ballistic resonant optical devices with adjustable transmission responses.
