Negative differential resistance due to the resonance coupling of a quantum-dot dimer

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Electron tunneling through a coupled quantum-dot dimer under a dc-bias is investigated. We find that a peak in the I-V curve appears at low temperature when two discrete electronic states in the two quantum dots are aligned with each other -- resonance coupling. This leads to a negative differential resistance. The peak height and width depend on the dot-dot coupling. At high temperature, the peak disappears due to thermal smearing effects.