U. Walter

Anomalous magnetoresistance in charge density wave compounds: Is NbSe3 unique?

Abstract The partially gapped charge density wave (CDW) conductor NbSe 3 displays a dramatic magnetoresistance in the lower CDW state. We have made magnetoresistance measurements on the related partially gapped CDW compounds ZrTe 3 and K 3 Cu 8 S 6 . Despite structural and electronic similarities of these materials to NbSe 3 , we find non-existent or very small magnetoresistance effects. These results suggest that the anomalous magnetoresistance observed in NbSe 3 may be limited to partially gapped chain-like CDW conductors that contain a depinnable CDW.

Scanning tunnelling microscopy of charge density waves in 1T-TaS2

Using a variable temperature scanning tunnelling microscope we have observed both the lattice and the triple charge density wave (CDW) in 1T‐TaS2. We obtained images of the nearly‐commensurate (NC) phase between 350 and 200 K and the triclinic (T) phase between 220 and 280 K. We analysed the images to determine the local angle of rotation of the CDW relative to the lattice to determine if commensurate domains exist in this material. In the NC phase we do not see the hexagonal discommensurate domains proposed by Nakanishi el al. (1977), but observe a structure which is uniformly incommensurate. The orientation of the CDW relative to the lattice is observed to be locally incommensurate and to vary continuously with temperature as reported by Scruby et al. (1975). However, in the T phase we observe long narrow commensurate domains very similar to those described by Nakanishi and Shiba (1984) for this phase.

Electronic interference, elasticity, and scanning tunneling microscopy studies of the charge density wave conductor K0.3MoO3

Abstract Charge density wave (CDW) dynamics and statics are explored in the blue bronze K 0.3 MoO 3 . For very thin (optically transparent, d≈0.2 μ m) platelets highly coherent response obtains, and in the presence of dc electric fields the ac conductivity shows high frequency interference structure. This interference is discussed in terms of a resonant circuit analog. At low temperatures, the zero differential resistance state is associated with dramatic changes in the elastic constants of the crystal. However, the effects of sample core heating may be important. Both above and below the CDW transition temperature, the surface of K 0.3 MoO 3 has been examined by atomic resolution scanning tunneling microscopy. Although the underlying lattice is clearly resolved, no CDW superstructure has been imaged on the crystal surface.