Capacitive detection of magnetic field induced quantum phase transitions in an imbalanced bilayer electron system

Ground states that appear in a quantizing magnetic field in an imbalanced bilayer electron system hosted by a dual-gated, wide GaAs quantum well are explored with a magnetocapacitance technique that enables detection of the compressibility of each layer separately, the characterization of the charge distribution, as well as the distinction of single- or double-layer-like behavior. Magnetic field induced reentrant quantum phase transitions are observed between a compressible double-layer ground state and a single-layer-like incompressible phase for both total fillings 1 and 2. The transitions are accompanied by a charge redistribution across the well. Our observations indicate for both incompressible states easy-plane pseudospin ferromagnetism as the origin.