Observation of Reentrant Phases Induced by Short-Range Disorder in the Lowest Landau Level of AlxGa1-xAs/Al0.32Ga0.68As Heterostructures

We report the observation of a reentrant quantum Hall effect in the lowest Landau level between filling factors of 2/3 and 3/5 in a AlxGa1-xAs/Al0.32Ga0.68As heterostructure sample with x 0.85%. A reentrant insulating phase is also observed between filling factors of 2/5 and 1/3, demonstrating particle-hole symmetry between these phases. A sample with x = 0.21% shows much weaker reentrant features, indicating that increased short-range scattering, due to the Al alloy in the conduction channel, aids in the formation of these phases.