Competing Phases of 2D Electrons at $\nu$ = 5/2 and 7/3

The N=1 Landau level (LL) exhibits collective electronic phenomena characteristic of both fractional quantum Hall (FQHE) states seen in the lowest LL and anisotropic nematic states in the higher LLs. A modest in-plane magnetic field $B_{||}$ is sufficient to destroy the fractional quantized Hall states at $\nu = 5/2$ (and 7/2) and replace them with anisotropic compressible nematic phases, revealing the close competition between the two. We find that at larger $B_{||}$ these anisotropic phases $\nu = 5/2$ can themselves be replaced by a new isotropic state, dubbed re-entrant isotropic compressible (RIC) phase. We present strong evidence that this transition is a consequence of the mixing of Landau levels from different electric subbands in the confinement potential. In addition, we find that with $B_{||}$, the normally isotropic $\nu = 7/3$ FQHE state can transform into an anisotropic phase with an accurately quantized Hall plateau but an anisotropic longitudinal resistivities. As temperature is lowered towards zero, $\rho_{xx}$ diminishes while $\rho_{yy}$ tends to diverge, reminiscent of the anisotropic nematic states, while surprisingly $\rho_{xy}$ and $\rho_{yx}$ remain quantized at $3h/7e^{2}$, indicating a completely new quantum phase.