Charge Density Wave Transitions Induced in Nb3Se4and Nb3S4by Indium Intercalation

The family of crystals Nb3X4(X=Te,Se,S) are isostructural, quasi one-dimensional tunnel structures. The telluride exhibits a charge density wave below room temperature, but no such transition occurs in the selenide or sulfide. A variety of foreign atoms can be intercalated into the tunnels of these structures and it is known that thallium intercalation in Nb3Te4causes dramatic changes in the charge density wave characteristics, due to changes in the Fermi surface and density of states resulting from the electrons being transferred to the host crystal from the intercalated atoms. In this paper it is shown that indium intercalation in Nb3Se4and Nb3S4gives rise to superlattice reflections in electron diffraction patterns, which are interpreted as being due to charge density waves. The unusual variations of the charge density wave vectors with intercalate concentration are discussed and a model to account for them is proposed.