SCANNING-TUNNELING-MICROSCOPY ANALYSIS OF THE CHARGE-DENSITY-WAVE STRUCTURE IN NBSE3

Nb-93 NMR and scanning-tunneling-microscopy (STM) studies lead to different conclusions on the question of which chains are involved in the formation of the two charge-density waves (CDW's) in NbSe3. To resolve this conflict, we calculated the STM images of a single NbSe3 layer and analyzed the local densities of states (LDOS) of Nb and Se atoms in the vicinity of the Fermi level. The conflict arises from the fact that Nb-93 NMR and STM measurements probe the LDOS of different atoms (Nb and Se atoms, respectively) at the Fermi level. Concerning the question of which chains are responsible for the CDW formation in NbSe3, however, the conclusion of the Nb-93 NMR studies is appropriate because the major character of the electrons at the Fermi level is the Nb atoms of type-I and -III chains.