NbS3: A unique quasi-one-dimensional conductor with three charge density wave transitions

We review the features of the charge density wave (CDW) conductor $\mathrm{Nb}{\mathrm{S}}_{3}$ (phase II) and include several additional results from transport, compositional, and structural studies. Particularly, we highlight three central results: (1) In addition to the previously reported CDW transitions at ${T}_{\mathrm{P}1}=360\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and ${T}_{\mathrm{P}2}=150\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, a third CDW transition occurs at a much higher temperature ${T}_{\mathrm{P}0}\ensuremath{\approx}620\ensuremath{-}650\phantom{\rule{0.16em}{0ex}}\mathrm{K}$; evidence for the nonlinear conductivity of this CDW is presented. (2) We show that the CDW associated with the ${T}_{\mathrm{P}2}$ transition arises from S vacancies acting as donors. Such a CDW transition has not been observed before. (3) We demonstrate the exceptional coherence of the ${T}_{\mathrm{P}1}$ CDW at room temperature. The effects of uniaxial strain on the CDW transition temperature and transport are reported.