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6 records were found.

## Anomalous robustness of the 5/2 fractional quantum Hall state near a sharp phase boundary

We report magneto-transport measurements in wide GaAs quantum wells with tunable density to probe the stability of the fractional quantum Hall effect at filling factor $\nu =$ 5/2 in the vicinity of the crossing between Landau levels (LLs) belonging to the different (symmetric and antisymmetric) electric subbands. When the Fermi energy ($E_F$) lies in the excited-state LL of the symmetric subband, the 5/2 quantum Hall state is surprisingly stable and gets even stronger near this crossing, and then suddenly disappears and turns into a metallic state once $E_F$ moves to the ground-state LL of the antisymmetric subband. The sharpness of this disappearance suggests a first-order transition.

## Spin and charge distribution symmetry dependence of stripe phases in two-dimensional electron systems confined to wide quantum wells

Measurements in clean two-dimensional electron systems confined to wide GaAs quantum wells in which two electric subbands are occupied reveal an unexpected rotation of the orientation of the stripe phase observed at a half-filled Landau level. Remarkably, the reorientation is sensitive to the spin of the half-filled Landau level and the symmetry of the charge distribution in the quantum well.

## Hole-flux Composite Fermion Commensurability Oscillations

Comment: 5 pages, 3 figures

## Reentrant nu = 1 quantum Hall state in a two-dimensional hole system

We report the observation of a reentrant quantum Hall state at the Landau level filling factor nu = 1 in a two-dimensional hole system confined to a 35-nm-wide (001) GaAs quantum well. The reentrant behavior is characterized by a weakening and eventual collapse of the nu = 1 quantum Hall state in the presence of a parallel magnetic field component B||, followed by a strengthening and reemergence as B|| is further increased. The robustness of the nu = 1 quantum Hall state during the transition depends strongly on the charge distribution symmetry of the quantum well, while the magnitude of B|| needed to invoke the transition increases with the total density of the system.

## Evolution of the 7/2 fractional quantum Hall state in two-subband systems

We report the evolution of the fractional quantum Hall state (FQHS) at even-denominator filling factor $\nu=7/2$ in wide GaAs quantum wells in which electrons occupy two electric subbands. The data reveal subtle and distinct evolutions as a function of density, magnetic field tilt-angle, or symmetry of the charge distribution. When the charge distribution is strongly asymmetric, there is a remarkable persistence of a resistance minimum near $\nu=7/2$ when two Landau levels belonging to the two subbands cross at the Fermi energy. The field position of this minimum tracks the 5/2 filling of the symmetric subband, suggesting a pinning of the crossing levels and a developing 5/2 FQHS in the symmetric subband even when the antisymmetric level is partially filled.

## Ballistic transport of (001) GaAs 2D holes through a strain-induced lateral superlattice

Comment: 5 pages, 4 figures