Charge density waves in NbSe3: The models and the experimental evidence

Abstract: Charge density wave (CDW) ordering in the prototypical low-dimensional compound NbSe3 is reconsidered. It is shown that the model with two incommensurate modulations, and , localized on type-III and type-I bi-capped trigonal prismatic columns, does not explain details, revealed by various microscopic methods. An alternative explanation, based on the existence of modulated layered nano-domains below both CDW onset temperatures, is suggested. It accounts for the presence of the modulation in the STM images recorded above the CDW transition and for the absence of satellites in the corresponding diffraction patterns. The long periodic modulation, detected by LT STM, is attributed to a beating between the two CDWs, centered on adjacent columns of the same type. Such pairs of alternatively modulated columns represent the basic modulation units, ordered into nano-domains. [ABSTRACT FROM AUTHOR]