  The impurity-related electron transport through a double quantum dot (QD)
Aharonov-Bohm (AB) interferometer is theoretically studied, by considering
impurities coupled to the QDs in the interferometer arms. When investigating
the linear conductance spectra \emph{vs} the impurity levels, we show that the
impurities influence the electron transport in a nontrivial way, since their
suppressing or enhancing the electron tunneling. A presented single-level
impurity leads to the appearance of Fano lineshapes in the conductance spectra
in the absence of magnetic flux, with the positions of Fano antiresonances
determined by both the impurity-QD couplings and the QD levels separated from
the Fermi level, whereas when a magnetic flux is introduced with the the phase
factor $\phi=\pi$ the impurity-driven Breit-Wigner lineshapes appear in the
conductance curves. Besides, the nonlocal impurities alter the period of
conductance change \emph{vs} the magnetic flux. The multi-level impurities
indeed complicate the electron transport, but for the cases of two identical
local impurities coupled to the respective QDs with uniform couplings or a
nonlocal impurity coupled to both QDs uniformly, the antiresonances are only
relevant to the impurity levels. When many-body effect is managed within the
second-order approximation, we also find the important role of the Coulomb
interaction in modifying the electron transport.
