Charge-density waves and localization in electron-irradiated1T−TaS2

The relations between electronic transport, the periodic lattice distortion (PLD) associated with charge-density waves (CDW), and disorder are studied experimentally in $1T-\mathrm{T}\mathrm{a}{\mathrm{S}}_2$. Disorder is introduced by means of electron irradiation which is able to displace lattice atoms. The effects stable around room temperature are due to displacements in the tantalum sublattice. The irradiation-induced defects act strongly on the CDW; they pin its phase and are thus able to suppress the phase transitions where the PLD orders to form a commensurate superstructure. The localized electronic ground state of the pure material can be destroyed by slight disorder to obtain metallic transport properties. Further irradiation-induced disorder leads to a new localization. This sequence is interpreted as a change from Mott to Anderson localization.