Enhanced Charge Order in a Photoexcited One-Dimensional Strongly Correlated System

We present a compelling response of a low-dimensional strongly correlated system to an external perturbation. Using the time-dependent Lanczos method we investigate a nonequilibrium evolution of the half-filled one-dimensional extended Hubbard model, driven by a transient laser pulse. When the system is close to the phase boundary, by tuning the laser frequency and strength, a sustainable charge order enhancement is found that is absent in the Mott insulating phase. We analyze the conditions and investigate possible mechanisms of emerging charge order enhancement. Feasible experimental realizations are proposed.

Figure 1

Time dependence of the charge-charge correlations as functions of distance (labeled by $j$) for 14-site lattice. The laser pulse with Gaussian magnitude modulation reaches its full strength at $t=12.5$, as indicated by solid lines. Without exception, the pumping frequencies are set to match the resonance peaks of the optical absorption spectrum. Parameters: $U=10$, $\delta t=0.02$, $M=100$. (a) $V=1.0$, ${\omega }_{\mathrm{pump}}=7.1$, $A_0=0.10$; (b) $V=3.0$, ${\omega }_{\mathrm{pump}}=6.1$, $A_0=0.30$; (c) $V=4.5$, ${\omega }_{\mathrm{pump}}=4.0$, $A_0=0.07$; (d) $V=5.5$, ${\omega }_{\mathrm{pump}}=4.1$, $A_0=0.60$.

Figure 2

The expectations of CDW order parameter of eigenstates for $10$-site lattice with $V=1.0$, 3.0, 4.5, and 5.5. The energy $E$ is measured from the ground state. Only the data of states with $P_{\mathrm{tot}}=S_{\mathrm{tot}}=0$ are shown, up to $E=60$. Note that the largest value of $⟨{\mathcal{O}}_{\mathrm{CDW}}⟩$ in (a) through (d) is marked by a cross.

Figure 3

Contour plots of final time-evolution results of CDW order $⟨{\mathcal{O}}_{\mathrm{CDW}}{⟩}_{\mathrm{av}}$ (first column) and energy increase $\Delta E$ (second column) as functions of ${\omega }_{\mathrm{pump}}$ and $A_0$, obtained by averaging on the last 50 time steps (time length $\Delta t=5$), for 10-site lattice. Here, we take $\delta t=0.1$, $M=30$. (a), (b) $V=1.0$; (c), (d) $V=3.0$; (e), (f) $V=4.5$; and (g), (h) $V=5.5$.

Figure 4

The imaginary part of the dynamical current-current correlation function for 10-site lattice with $V=1.0$, 3.0, 4.5, and 5.5, obtained by Lanczos method. The $\delta$ function is approached by a Lorentzian with a width of 0.1.