Structure factor of a charge-density wave

Abstract

The elastic structure factor of an unpinned charge-density wave (CDW) is derived. Both phase and amplitude excitations are studied. Phase modes cause a reduction of the intensity of CDW satellite peaks of any order. Amplitude modes, however, do not alter appreciably the intensity of the first-order CDW satellite. In fact, they enhance the intensity of peaks of higher order on account of their nonlinear nature. Neither phase nor amplitude excitations affect the usual Bragg reflections. The mean-square fluctuation of the CDW phase and the associated reduction of the satellite peaks are discussed for the case of potassium and are shown to depend critically on the phason spectrum.