Non-equilibrium dynamics across the BEC-BCS crossover

Abstract

We investigate the quench dynamics of strongly coupled superconductors within the time-dependent Gutzwiller approximation from the BCS to the BEC regime and evaluate the out-of-equilibrium transient spectral density and optical conductivity relevant for pump probe experiments. Fourier transformation of the order parameter dynamics reveals a frequency ${\Omega }_J$ which, as in the BCS case, is controlled by the spectral gap. However, we find a crossover from the BCS dynamics to a new strong coupling regime where a characteristic frequency ${\Omega }_U$, associated to double occupancy fluctuations controls the order parameter dynamics. The change of regime occurs close to a dynamical phase transition. Both, ${\Omega }_J$ and ${\Omega }_U$ give rise to a complex structure of self-driven slow Rabi oscillations which are visible in the non-equilibrium optical conductivity where also side bands appear due to the modulation of the double occupancy by superconducting amplitude oscillations. Analogous results apply to CDW and SDW systems.

14 pages, 14 figures

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• Engineering Higgs dynamics by spectral singularities
• Long-lived Higgs modes in strongly correlated condensates
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• Adiabatic transition from a BCS superconductor to a Fermi liquid and phase dynamics
• Optical absorption activated by an ultrashort half-cycle pulse in metallic and superconducting states of the Hubbard model