(a) Schematic of the capacitively side-coupled DQD, where QD1 and QD2 couple with each other through the interdot Coulomb interaction U₁₂, but only QD1 couples directly to reservoirs L and R with hybridization Γ_L and Γ_R, respectively. (b) Schematic view of the removal of degeneracy to the S-O (singly-occupied) and D-O (doubly-occupied) states by U₁₂. At very low temperature, the S-O₂ and S-O₁ substates go through ϵ_F as U₁₂ increases, and then interact with the Kondo resonance to induce Kondo–Fano interference.