Photon-assistant Fano resonance in serially coupled triple quantum dots

Based on calculations of the electronic structure of serially coupled triple quantum dots ( left, middle, right dots) (STQDs), we study the transport properties of the system driven by an ac electric field. It is found that the Lambda-type energy level of STQDs has great impact on the transport properties. For an asymmetric ( between left and right dots) configuration, there is a symmetric peak in the current-AC frequency curve due to resonant photon induced mixing between the left/ right dot and the middle dot. In the symmetric ( between left and right dots) configuration, a Fano asymmetric line shape appears in the current-frequency curve with the help of a 'trapping dark state'. Here the interesting coherent trapping phenomena, which usual appear in quantum optics, play an essential role in quantum electronic transport. We provide a clear physics picture for the Fano resonance and convenient ways to tune the Fano effects.