Search for charge density waves in potassium

Abstract

Motivated by the recent calculation of Guiliani and Overhauser in which a criterion for the preferred orientation of the wave vector $\overrightarrow{\mathrm{Q}}$ of a charge density wave (CDW) in the alkali metals was derived, we have carried out a neutron-diffraction search for CDW's in potassium metal. Although the search was not exhaustive of all the possibilities, we have been unable to detect any satellite peaks at (or near) the predicted positions in reciprocal space. However, we have found small diffraction peaks along certain symmetry axes at other positions in reciprocal space. They are strongly temperature dependent, resembling the Debye-Waller effect in potassium metal, but they do not satisfy the symmetry requirements of a CDW modulation of the body-centered-cubic crystal structure.