Charge density wave transitions induced in Nb3Se4 and Nb3S4 by indium intercalation

The family of crystals Nb3X4 (X = Te, Se, S) are isostructural, quasi one-d imensional tunnel structures, The telluride exhibits a charge density wave below room temperature, but no such transition occurs in the selenide or su lfide, A variety of foreign atoms can be intercalated into the tunnels of t hese structures and it is known that thallium intercalation in Nb3Te4 cause s dramatic changes in the charge density wave characteristics, due to chang es 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 Nb3Se4 and Nb3S4 gives rise to superlattice reflections in electron diffraction patterns, which are int erpreted as being due to charge density waves. The unusual variations of th e charge density wave vectors with intercalate concentration are discussed and a model to account for them is proposed. (C) 1999 Academic Press.