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In pump-probe experiments the real-time dynamics of interacting electrons is measured by first driving the sample out of equilibrium with a pump pulse, and then probing its state with a second pulse after a controlled time delay. In time-resolved (TR) optical spectroscopy the reflected electrical field is measured, whereas in TR photoemission spectroscopy the spectrum of the emitted electrons is analyzed. These experimental signals can be related to the two-time optical conductivity and to the real-time electronic Green function, respectively. Both quantities can be calculated using nonequilibrium dynamical mean-field theory (DMFT), which maps an interacting lattice system onto an effective time-dependent single-site problem. TR optical spectroscopy has the advantage of full time resolution [1], whereas TR photoemission spectroscopy provides momentum resolution of the electronic Green functions but suffers from some energy-time uncertainty restrictions [2]. We present explicit results for the Falicov-Kimball model [1,2], for which we model the pump excitation by a sudden parameter change in the Hamiltonian [3]. We identify characteristic signatures in the experimental signals, e.g., for as-yet-unobserved electronic collapse-and-revival oscillations, the type of which are well-known from cold atom experiments. [1] M. Eckstein and M. Kollar, Phys. Rev. B 78, 205119 (2008). [2] ibid., 245113. [3] Phys. Rev. Lett. 100, 120404 (2008). |
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