We study the anisotropic pinning-mode resonances in the rf conductivity spectra of the stripe phase of 2D electron systems around a Landau level filling of $9/2$, in the presence of an in-plane magnetic field $B_{\mathrm{ip}}$. The polarization along which the resonance is observed switches as $B_{\mathrm{ip}}$ is applied, consistent with the reorientation of the stripes. The resonance frequency, a measure of the pinning interaction between the 2D electron systems and disorder, increases with $B_{\mathrm{ip}}$. The magnitude of this increase indicates that disorder interaction is playing an important role in determining the stripe orientation.

• Received 20 October 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.136804