Density-Induced Interchange of Anisotropy Axes at Half-Filled High Landau Levels

We observe density-induced [Formula presented] rotations of the anisotropy axes in transport measurements at half-filled high Landau levels in the two dimensional electron system, where stripe states are proposed ([Formula presented], [Formula presented], etc.). Using a field effect transistor, we find the transition density to be [Formula presented] at [Formula presented]. Hysteresis is observed in the vicinity of the transition. We construct a phase boundary in the filling factor magnetic field plane in the regime [Formula presented]. An in-plane magnetic field applied along either anisotropy axis always stabilizes the low density orientation of the stripes.