Huge longitudinal resistance maxima at fractional filling factors

Very large resistance maxima can be observed in the longitudinal magnetoresistance of a narrow single quantum well. They exist only at certain fractional filling factors and are clearly related to the coupling of the electron to the nuclear spin system. In resistively detected NMR experiments, which are possible in this system, a very unusual fine structure of the resonance lines is observed, which hints towards an unusual coupling between the electron and nuclear system.     

Superfluidity of indirect excitons vs quantum Hall correlation in double Hall systems: Different types of physical mechanisms of correlation organization in Hall bilayers

Bilayer Hall systems can be divided into two groups—with and without tunneling of carriers across the barrier between layers. We demonstrate that these both classes differ in topology sense which leads to the distinct quantum Hall hierarchy. In the case of forbidden interlayer carrier tunneling we developed the Metropolis Monte Carlo simulation for an energy competition of the reentrant integer quantum Hall state against the superfluid Bose Einstein condensate of indirect excitons in double-layer 2D Hall systems, GaAs/GaAlAs/GaAs and b-graphene/hBN/b-graphene, with complementary layer filling, ${\nu }_{bot}+{\nu }_{top}=1$. The resulted phase diagrams for both systems have been determined in consistence with the experimental data.