  Electron-phonon-driven charge density waves can in some circumstances allow
electronic correlations to become predominant, driving a system into a Mott
insulating state. New insights into both the Mott state and preceding charge
density wave may result from observations of the coupled dynamics of their
underlying degrees of freedom. Here, tunneling injection of single electrons
into the upper Hubbard band of the Mott charge-density-wave material 1T-TaS2
reveals extraordinarily narrow electronic excitations which couple to amplitude
mode phonons associated with the charge density wave's periodic lattice
distortion. This gives a vivid microscopic view of the interplay between
excitations of the Mott state and the lattice dynamics of its charge density
wave precursor.
