Two- and three-electron bubbles in AlxGa1-xAs/Al0.24Ga0.76As quantum wells

We report on transport signatures of eight distinct bubble phases in the N = 3 Landau level of an AlxGa1-xAs/Al0.24Ga0.76As quantum well with x = 0.0015. These phases occur near partial filling factors nu* approximate to 0.2 (0.8) and nu* approximate to 0.3 (0.7) and have M = 2 and M = 3 electrons (holes) per bubble, respectively. We speculate that a small amount of alloy disorder in our sample helps to distinguish these broken symmetry states in low-temperature transport measurements.