Electronic transport through a double-quantum-dot Aharonov-Bohm interference device with impurities

TL;DR

This paper theoretically investigates how impurities affect electron transport in a double quantum dot Aharonov-Bohm interferometer, revealing complex Fano and Breit-Wigner lineshapes and the influence of Coulomb interactions.

Contribution

It introduces a detailed theoretical analysis of impurity effects on electron transport in a double quantum dot AB interferometer, including multi-level impurities and Coulomb interactions.

Findings

Impurities cause Fano and Breit-Wigner lineshapes in conductance spectra.

Impurities alter the period of conductance oscillations with magnetic flux.

Coulomb interactions significantly modify electron transport behavior.

Abstract

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.