This Letter theoretically validated that the $\omega =0$ component of a photoexcited Drude peak in one-dimensional Mott insulators is nonzero only when a finite amount of charge fluctuations is included. Here, we define charge fluctuations as annihilations and creations of photoexcited elementary particles, that are, holons (Hs) and doublons (Ds). In contrast, when the electron on-site repulsion, $U$, is infinite, such fluctuations are completely suppressed, and the H and D behave, such as rigid balls, leading to a vanishing $\omega =0$ component. Such behaviors inspire us to name them as “quantum clackers.” Moreover, we demonstrated that the effective broadenings of the finite-frequency components of the Drude peak are affected by charge fluctuations and carrier density. Finally, we discovered that such broadenings can be estimated using the group velocity of the relative motion of an H and a D as would be predicted from a colliding picture of the two particles.

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• Electrical conductivity
• Optical conductivity
• 1-dimensional systems
• Effective field theory