Magnetic-field effects on transport in carbon nanotube junctions

TL;DR

This paper presents a theoretical analysis of how magnetic fields influence electronic transport in carbon nanotube heterojunctions and quantum dots, revealing oscillations in conductance gaps without Aharonov-Bohm periodicity.

Contribution

It introduces a detailed tight-binding model incorporating atomic topological defects and magnetic effects to study conductance in carbon nanotube heterostructures.

Findings

Conductance gap oscillates with magnetic flux.

Oscillations differ from Aharonov-Bohm periodicity.

Atomic defect details affect magnetic response.

Abstract

Here we address a theoretical study on the behaviour of electronic states of heterojunctions and quantum dots based on carbon nanotubes under magnetic fields. Emphasis is put on the analysis of the local density of states, the conductance, and on the characteristic curves of current versus voltage. The heterostructures are modeled by joining zigzag tubes through single pentagon-heptagon pair defects, and described within a simple tight binding calculation. The conductance is calculated using the Landauer formula in the Green functions formalism. The used theoretical approach incorporates the atomic details of the topological defects by performing an energy relaxation via Monte Carlo calculation. The effect of a magnetic field on the conductance gap of the system is investigated and compared to those of isolated constituent tubes. It is found that the conductance gap of the studied CNHs exhibits oscillations as a function of the magnetic flux. However, unlike the pristine tubes case, they are not Aharonov-Bohm periodic oscillations.