New results at half-fillings in the second and third Landau level

This paper presents some recent results on the anisotropic electronic transport at half-filling factors in the second and third Landau levels. In the third Landau level at ν = 9/2 and 11/2, the electronic transport is already strongly anisotropic in perpendicular magnetic field. This anisotropic phase is believed to be due to the formation of a unidirectional charge density wave. Applying an in-plane field overcomes the initial pinning and reorients the direction of this anisotropy. In the second Landau level, the even-denominator fractional quantum Hall state at ν = 5/2 and 7/2 is destroyed and transformed into an anisotropic phase by an in-plane magnetic field. This result provides additional evidence that the ground state at ν = 5/2 and 7/2 is spin-polarized.