Electronic transport across a junction between armchair graphene nanotube and zigzag nanoribbon Transmission in an armchair nanotube without a zigzag half-line of dimers

• Published in: The European physical journal. B, Condensed matter physics Vol. 91; no. 5
• Main Author: Sharma, Basant Lal
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2018; Springer
• Subjects: Analysis; Complex Systems; Condensed Matter Physics; Electrons; Fluid- and Aerodynamics; Graphene; Graphite; Nanotubes; Physics; Physics and Astronomy; Regular Article; Solid State Physics; Wave propagation; Solid State and Materials
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2018-80647-2

Based on the well known nearest-neighbor tight-binding approximation for graphene, an exact expression for the electronic conductance across a zigzag nanoribbon/armchair nanotube junction is presented for non-interacting electrons. The junction results from the removal of a half-row of zigzag dimers in armchair nanotube, or equivalently by partial rolling of zigzag nanoribbon and insertion of a half-row of zigzag dimers in between. From the former point of view, a discrete form of Dirichlet condition is imposed on a zigzag half-line of dimers assuming the vanishing of wave function outside the physical structure. A closed form expression is provided for the reflection and transmission moduli for the outgoing wave modes for each given electronic wave mode incident from either side of the junction. It is demonstrated that such a contact junction between the nanotube and nanoribbon exhibits negligible backscattering, and the transmission has been found to be nearly ballistic. In contrast to the previously reported studies for partially unzipped carbon nanotubes (CNTs), using the same tight binding model, it is found that due to the “defect” there is certain amount of mixing between the electronic wave modes with even and odd reflection symmetries. But the junction remains a perfect valley filter for CNTs at certain energy ranges. Applications aside from the electronic case, include wave propagation in quasi-one-dimensional honeycomb structures of graphene-like constitution. The paper includes several numerical calculations, analytical derivations, and graphical results, which complement the provision of succinct closed form expressions.