Nonequilibrium $GW+\mathrm{EDMFT}$: Antiscreening and Inverted Populations from Nonlocal Correlations

We study the dynamics of screening in photodoped Mott insulators with long-ranged interactions using a nonequilibrium implementation of the $GW$ plus extended dynamical mean-field theory formalism. Our study demonstrates that the complex interplay of the injected carriers with bosonic degrees of freedom (charge fluctuations) can result in long-lived transient states with properties that are distinctly different from those of thermal equilibrium states. Systems with strong nonlocal interactions are found to exhibit a self-sustained population inversion of the doublons and holes. This population inversion leads to low-energy antiscreening which can be detected in time-resolved electron-energy-loss spectra.

Figure 1

Equilibrium results for $U=10.5$, $V=1.5$, and $\beta =20$. (a) Comparison of the Matsubara time component of the Green’s function $G^{\text{Mat}}(\tau )$ obtained from NCA, OCA, and numerically exact Monte Carlo simulations for $U=10.5$. (b) Spectral functions obtained from different approximations. Solid (dashed) lines correspond to the NCA (OCA) solution. (c) Imaginary part of the screened interaction $W(\omega )$ obtained from different approximations. (d) Double occupation $n_d$ near the metal-insulator transition or crossover. A coexistence region exists in the OCA.

Figure 2

Time evolution of the double occupancy $n_d$ (a) and kinetic energy (b) after the photoexcitation in EDMFT (dashed lines) and $GW+\mathrm{EDMFT}$ (solid lines) for different nonlocal interactions $V$ at fixed density $\mathrm{\Delta }{n}_d=0.01$ of photoexcited carriers after the pulse. The local interaction is $U=10.5$.

Figure 3

(a) Time evolution of the spectral function (solid lines) and occupation (dashed lines) after the electric field excitation. (b) The distribution function illustrates the evolution into the self-sustained inverted population state. (c) Distribution functions for $t_{\max }=24$ and different excitation strengths. (d) Time evolution of the screened interaction $W^R(t,\omega )$ (solid lines) and its lesser component (boson occupancy, dashed lines) $W^{<}(t,\omega )$ in the inverted population regime. (e) Imaginary part of the impurity effective interaction $\mathrm{Im}[D^R(t_{\max },\omega )]$ in EDMFT (dashed lines) and $GW+\mathrm{EDMFT}$ (solid lines) for different excitations strengths. The pulse frequency is $\omega =U=10.5$, the pulse amplitude is $E_0=2$ [except in (c)], and $V=1.5$.

Figure 4

Top panels: Imaginary part of the inverse dielectric function $-\mathrm{Im}[{ϵ}_q^{-1}(\omega )]$ obtained in the Hubbard I approximation for the thermal (a) and nonthermal (c) distribution functions shown in (b). Bottom panels: $GW+\mathrm{EDMFT}$ results for $-\mathrm{Im}[{ϵ}_q^{-1}(t,\omega )]$ in equilibrium (d) and in the photoexcited system at indicated time delays (e)–(h). The pulse frequency is $\omega =U=10.5$, the pulse amplitude is $E_0=2$, and $V=1.5$.