Scanning tunneling microscopy of the charge-density wave in orthorhombic TaS3

Scanning tunneling microscopy has been used to study the charge-density wave (CDW) in o-TaS3. Above the Peierls transition temperature, Tp=215 K, charge modulations are observed that exhibit temporal fluctuations in modulation amplitude and periodicity. As the temperature is lowered, the fluctuations diminish and a more ordered structure is observed. Below the transition temperature the CDW superlattice forms, revealing an approximate 4c0×10b0 structure in good agreement with electron diffraction experiments. In addition, each unit cell is seen to contain two uniformly distributed CDW maxima along b0, suggesting that the CDW in this material is not highly localized to only two of the chains of the unit cell.