Ultrafast Optical Responses in a One-Dimensional Mott Insulator of a Br-Bridged Ni Compound

Abstract

We investigated the ultrafast optical responses of a one-dimensional (1D) Mott insulator by applying fs pump–probe absorption spectroscopy on a thin film sample of a Br-bridged Ni compound. Transient absorption changes and their excitation-energy dependences reveal that the responses consist of three components; coherent responses, responses of excitons and charge carriers. The decay time of excitons is very small (∼1.4 ps), which is characteristic of 1D Mott insulators. The relatively slow relaxation of charge carriers with several tens of picoseconds is attributable to polaronic effects.