Structural instabilities in Nb, Ti and K substituted BaVS 3

The one-dimensional (1D) strongly correlated BaVS ₃ undergoes a series of unexplained phase transitions. Among them it undergoes a metal-insulator (MI) transition associated with a 2k_F=c^*/2 charge density wave (CDW) instability. We show that this CDW ground state is very sensitive to chemical substitutions and/or sulfur deficiency. Substitutions of V with ≈2% of Nb, Ti or Ba with ≈2% K in probably sulfur deficient samples leads to a completely different ground state. This ground state is characterized by a short range structural modulation with the incommensurate wave vector q_S=({1}/{3} {1}/{3} 0.21)_H, which could be due to a CDW taking place in a differently filled d band.