Nonequilibrium dynamics and coherent control of BCS superconductors driven by ultrashort THz pulses

Abstract

The nonequilibrium dynamics of BCS superconductors after excitation with short THz pulses slightly above the superconducting gap is studied theoretically. Calculated pump-probe spectra show how the gap is influenced by this optical excitation. For ultrashort pump pulses a nonadiabatic regime emerges, in which the BCS order parameter exhibits oscillations. These oscillations do not show up in pump-probe spectra. However they may be made visible by using a coherent control type excitation with two phase-locked pump pulses. © 2009 IOP Publishing Ltd.