X-ray scattering studies of charge-density waves in tantalum disulfide

Abstract

The temperature dependence of the wave vectors and intensities of the charge-density-wave satellites in 1T-${\mathrm{TaS}}_2$ have been investigated in detail in the noncommensurate (NC) and incommensurate (IC) phases with the use of x-ray precession photography and counter measurements. In the IC phase (T≥80°C) the intensities of first-order satellites are found to vary smoothly, and have led to the establishment of a ‘‘phason temperature factor.’’ In the NC phase, temperature-dependent domain structures have been found which prevent quantitative studies as a function of temperature. Second- and higher-order satellites are found to be, at room temperature, several orders of magnitude more intense than the values predicted by the simple sinusoidal model. It is suggested that in the NC phase several harmonics are present, which, however, disappear in the IC phase. It is found that in this phase the sinusoidal model is well applicable.