Pinning mode resonances of two-dimensional electron stripe phases at high Landau levels

This paper presents the radio-frequency (rf) diagonal conductivity spectra of two-dimensional electrons in the second excited and higher Landau levels, and in particular shows isotropic pinning mode resonances in the bubble phases evolving into a highly anisotropic rf resonance in the stripe phase. The stripe phase resonance is observed for the rf electric field, E(rf), along the ``hard{''} direction, in which the dc higher resistivity occurs, but not for E(rf) along the orthogonal, ``easy{''} direction. The resonance is naturally interpreted as a pinning mode of the stripe phase. (C) 2008 Elsevier B.V. All rights reserved.