By applying an unrestricted Hartree-Fock and a random phase approximation to a multiband Peierls-Hubbard Hamiltonian, we study the phonon mode structure in models of transition metal oxides in the presence of intrinsic nanoscale inhomogeneities induced by hole doping. We identify low-frequency local vibrational modes pinned to the sharp interfaces between regions of distinct electronic structure (doped and undoped) and separated in frequency from the band of extended phonons. A characteristic of these “edge” modes is that their energy is essentially insensitive to the doping level. We discuss the experimental manifestations of these modes in inelastic neutron scattering and also in spin and charge excitation spectra.

• Received 18 August 2004

DOI:https://doi.org/10.1103/PhysRevB.70.224514