Two- and three-electron bubbles in Al${}_x$Ga${}_{1-x}$As/Al${}_{0.24}$Ga${}_{0.76}$As quantum wells

Abstract

We report on transport signatures of eight distinct bubble phases in the $N=3$ Landau level of a Al${}_x$Ga${}_{1-x}$As/Al${}_{0.24}$Ga${}_{0.76}$As quantum well with $x=0.0015$. These phases occur near partial filling factors $\hat{I}{½}^{\star }\approx 0.2(0.8)$ and $\hat{I}{½}^{\star }\approx 0.3(0.7)$ 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.

4 pages