  An interacting bilayer electron system provides an extended platform to study
electron-electron interaction beyond single layers. We report here experiments
demonstrating that the layer densities of an asymmetric bilayer electron system
oscillate as a function of perpendicular magnetic field that quantizes the
energy levels. At intermediate fields, this interlayer charge transfer can be
well explained by the alignment of the Landau levels in the two layers. At the
highest fields where both layers reach the extreme quantum limit, however,
there is an anomalous, enhanced charge transfer to the majority layer.
Surprisingly, when the minority layer becomes extremely dilute, this charge
transfer slows down as the electrons in the minority layer condense into a
Wigner crystal. Furthermore, by examining the quantum capacitance of the dilute
layer at high fields, the screening induced by the composite fermions in an
adjacent layer is unveiled. The results highlight the influence of strong
interaction in interlayer charge transfer in the regime of very high fields and
low Landau level filling factors.
