Probing the coupling between a doublon excitation and the charge-density wave in TaS2 by ultrafast optical spectroscopy

TL;DR

This study uses broadband ultrafast spectroscopy to explore how doublon excitations interact with charge-density waves in 1T-TaS2, revealing strong coupling between specific charge excitations and the CDW state.

Contribution

It uncovers the coupling between doublon excitations and the charge-density wave in 1T-TaS2 using energy-dependent ultrafast optical spectroscopy.

Findings

Strong coupling between the amplitude mode and doublon states.

Doublon states are photoinduced in charge-ordered Ta clusters.

Energy-dependent excitation reveals interactions with the CDW.

Abstract

Recently, the switching between the different charge-ordered phases of 1T-TaS2 has been probed by ultrafast techniques, revealing unexpected phenomena such as "hidden" metastable states and peculiar photoexcited charge patterns. Here, we apply broadband pump-probe spectroscopy with varying excitation energy to study the ultrafast optical properties of 1T-TaS2 in the visible regime. By scanning the excitation energy in the near-IR region we unravel the coupling between different charge excitations and the low-lying charge-density wave state. We find that the amplitude mode of the charge-density wave exhibits strong coupling to a long-lived doublon state that is photoinduced in the center of the star-shaped charge-ordered Ta clusters by the near-IR optical excitation.