Vibrational edge modes in intrinsically heterogeneous doped transition metal oxides

TL;DR

This paper investigates vibrational edge modes in doped transition metal oxides, revealing localized phonon modes at interfaces caused by nanoscale inhomogeneities, with implications for experimental detection.

Contribution

It introduces the concept of vibrational edge modes localized at interfaces in doped transition metal oxides, highlighting their insensitivity to doping levels and potential experimental signatures.

Findings

Identification of low frequency vibrational modes at interfaces

Edge modes are insensitive to doping level

Potential detection in neutron scattering and spectra

Abstract

By applying an unrestricted Hartree-Fock and a Random Phase approximations 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.