Doublonlike Excitations and Their Phononic Coupling in a Mott Charge-Density-Wave System

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 insight 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 material1T−TaS2reveals 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.