Dephasing and interwell transitions in double quantum well heterostructures

The interference quantum correction to the conductivity in the gated double quantum well Al${}_x$Ga${}_{1-x}$As/GaAs/Al${}_x$Ga${}_{1-x}$As structures is studied experimentally. The consistent analysis of the interference induced positive magnetoconductivity allows us to find the interwell transition time ${\tau }_{12}$ and the electron dephasing time ${\tau }_{\varphi }$. It has been obtained that ${\tau }_{12}^{-1}$ resonantly depends on the difference between the electron densities in the wells as predicted theoretically. The dephasing times have been determined under the conditions when one and both quantum wells are occupied. The surprising result is that the ${\tau }_{\varphi }$ value in the one well does not depend on the occupation of the other one.