Vertical confinement and evolution of reentrant insulating transition in the fractional quantum Hall regime

We have observed an anomalous shift of the high field reentrant insulating phases in a two-dimensional electron system (2DES) tightly confined within a narrow GaAs/AlGaAs quantum well. Instead of the well-known transitions into the high field insulating states centered around $\nu =1/5,$ the 2DES confined within an 80-Å-wide quantum well exhibits the transition at $\nu =1/3.\mathrm{}$ Comparably large quantum lifetime of the 2DES in narrow well discounts the effect of disorder and points to confinement as the primary driving force behind the evolution of the reentrant transition.