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.