Strongly Anisotropic Electronic Transport at Landau Level Filling Factorν=9/2andν=5/2under a Tilted Magnetic Field

Abstract

We have investigated the influence of an increasing in-plane magnetic field on the states of half filling of Landau levels ( $\nu =11/2\mathrm{}$, 9/2, 7/2, and 5/2) of a two-dimensional electron system. In the electrically anisotropic phase at $\nu =9/2\mathrm{}$ and 11/2 an in-plane magnetic field of $\sim 1–2\mathrm{T}$ overcomes its initial pinning to the crystal lattice and reorients this phase. In the initially isotropic phases at $\nu =5/2\mathrm{}$ and 7/2 an in-plane magnetic field induces a strong electrical anisotropy. In all cases, for high in-plane fields the high-resistance axis is parallel to the direction of the in-plane field.