Pinning mode resonances of 2D electron stripe phases: Effect of an in-plane magnetic field

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 Bip. The polarization along which the resonance is observed switches as Bip 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 Bip. The magnitude of this increase indicates that disorder interaction is playing an important role in determining the stripe orientation.