Photoinduced Drude weights critically enhanced by charge fluctuations in a one-dimensional Mott insulator

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.

Figure 1

Schematic of metallic states in a 1D Mott insulator induced by hole doping and photodoping. The wavy line represents irradiated light. $U$ and $T$ denote the strength of the on-site Coulomb interaction and transfer energy, respectively. The curved arrows represent the motions of H and D. The electric field of the probe pulse is denoted as $E$.

Figure 2

Optical conductivity spectra of the photoexcited states of the pure HD model for $V=0$ and $\gamma =0.05T$. (a) ${\sigma }_{\mu }\left(\omega \right)$ at $\mu =N/8$ for the system size of $N=16$ (red), $N=32$ (green), and $N=64$ (blue). (b) ${\sigma }_{\mu }\left(\omega \right)$ at $N=64$ for $1\le \mu \le N/2-1$. The gray horizontal line corresponds to the same spectrum with $N=64$ in (a). The black lines in (b) exhibit $\omega =\pm (2m-1)(\pi /N)v_g^{-}\left(k_{\mu }\right)$ for $m=1–5$.

Figure 3

Optical properties of the third-order perturbative effective model (extended HD model) obtained from a charge model. (a) $U$ dependency of $K_{\mu }$ with $V=0$ at $N=64$. (b) $U$ dependency of $D_{\mu }$ with $V=0$ at $N=64$. (c) ${\sigma }_{\mu }\left(\omega \right)$ for $U=10T, V=0$, and $\gamma =0.05T$ at $\mu =N/8$. The colors are corresponding to the system size of $N=16$ (red), $N=32$ (green), and $N=64$ (blue). The whole $\mu$ dependency is shown in (d) for $N=64$. The gray horizontal line corresponds to the same spectrum with $N=64$ in (b). The black lines exhibit $\omega =\pm (2m-1)(\pi /N)v_g^{-}\left(k_{\mu }\right)$ for $m=1–5$.

Figure 4

${\sigma }_{\mu }\left(\omega \right)$ calculated by the extended HD model with $U=10T, V=2.4T, V_{\alpha \ge 4}=0, N=64$, and $\gamma =0.05T$ at $\mu =N$/8 (blue line). The red line is the corresponding result obtained for the pure HD model. The black dashed line for $V=0$, which is the same as the blue line in Fig. 3, is shown for comparison.