Resonant resistance enhancement in double-quantum-well GaAs-${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As heterostructures

We present a study of electron transport in coupled quantum-well structures controlled by both front and back gates. The resonant resistance enhancement is systematically investigated by varying the mobility in each quantum well. We show that a large mobility ratio between the two wells gives a large resonant resistance enhancement only when the level broadening is smaller than the symmetric-antisymmetric gap of the coupled system.