New lights on the ground-state phase diagrams of bilayer electron systems

K. MURAKI; P. GIUDICI

Lucca

Conferencia; Emergent Phenomena in Quantum Hall Systems 3; 2009

We present quasiparticle gap measurements in bilayer system at filling factor 1 [1] in thelimit of negligible interlayer tunneling and under a tilted magnetic field. Although our previous work has shown that the phase boundary separating the quantum-Hall and compressible states depends on the Zeeman energy [2], we observe that away from the phase boundary the activation gap is Zeeman independent. Our results clearly demonstrate that the quasiparticle excitation gap is of purely pseudospin origin and only governed by the competition of the inter- and intra-layer correlations, with its magnitude bearing a precise relation with the difference between the energies of the quantum Hall and the fully polarized compressible state. Our experimental results are successfully described using a simple model based on exciton formation, which assumes that the QH state forms from the compressible state as the condensation of excitons takes place. The implications of the model on the QH state as well as on the nature of the phase transition are discussed.