Missing integral quantum Hall effect in a wide single quantum well

We report magnetotransport measurements in a weakly coupled double-layer electron system realized in a wide quantum well. This system has the unique property that the distance and the coupling between the layers can be changed continuously by varying the electron density in the well. We observe the absence of quantum Hall states at odd filling factors. Our results complement earlier experimental work and are consistent with a recent theoretical model proposed for the magnetic-field-driven destruction of the quantum Hall effect in double quantum wells.