Charge fluctuations in a perfect and disturbed quantum wire

The tight-binding Hamiltonian and retarded Green function formalism are used to study the local and total density of states of a monatomic quantum wire. An additional atom (adatom) can be coupled with the wire at its side. Also the local and average charges of the perfect and disturbed wire are shown and the analytical formula for the local density of states at each site is obtained. The local density of states at each atom in a wire which consists of an even number of atoms is characterized by minima at the Fermi level, in comparison with a wire disturbed by an adatom, where the density of states is characterized by local peaks. Charge fluctuations (waves) are observed in the wire for the case when the condition for the conductance oscillations is satisfied. For the single electron energies of a wire localized above the Fermi energy the local charge along the wire forms a wave curve which possesses one maximum less than for energies localized below the Fermi level