  Using a perturbative approach, the effects of the energy gap induced by the
Aharonov-Bohm (AB) flux on the transport properties of defective metallic
single-walled carbon nanotubes (MSWCNTs) are investigated. The electronic waves
scattered back and forth by a pair of impurities give rise to Fabry-Perot
oscillations which constitutes a coherent backscattering interference pattern
(CBSIP). It is shown that, the CBSIP is aperiodically modulated by applying a
magnetic field parallel to the nanotube axis. In fact, the AB-flux brings this
CBSIP under control by an additional phase shift. As a consequence, the extrema
as well as zeros of the CBSIP are located at the irrational fractions of the
quantity $\Phi_\rho={\Phi}/{\Phi_0}$, where $\Phi$ is the flux piercing the
nanotube cross section and $\Phi_{0}=h/e$ is the magnetic quantum flux. Indeed,
the spacing between two adjacent extrema in the magneto-differential
conductance (MDC) profile is decreased with increasing the magnetic field. The
faster and higher and slower and shorter variations is then obtained by
metallic zigzag and armchair nanotubes, respectively. Such results propose that
defective metallic nanotubes could be used as magneto-conductance switching
devices based on the AB effect.
