Coherent dynamics of V-type systems driven by time-dependent incoherent radiation

TL;DR

This paper analytically investigates how time-dependent incoherent light affects V-type quantum systems, revealing the conditions under which radiative coherence persists or vanishes, with implications for natural light-induced processes.

Contribution

The study introduces a new master equation approach to analytically solve for the dynamics of V-type systems under time-dependent incoherent excitation, highlighting the impact of turn-on times on coherence.

Findings

Radiative coherence disappears when light turn-on times exceed system times.

Turn-on times longer than 1 ms can induce Fano coherences between nearly degenerate states.

Coherence effects are negligible for energy level separations greater than 0.9 cm$^{-1}$.

Abstract

Light induced processes in nature occur by irradiation with slowly turned-on incoherent light. The general case of time-dependent incoherent excitation is solved here analytically for V-type systems using a newly developed master equation method. Clear evidence emerges for the disappearance of radiatively induced coherence as turn-on times of the radiation exceed characteristic system times. The latter is the case, in nature, for all relevant dynamical time scales for other than nearly degenerate energy levels. We estimate that, in the absence of non-radiative relaxation and decoherence, turn-on times slower than 1 ms (still short by natural standards) induce Fano coherences between energy eigenstates that are separated by less than 0.9 cm$^{-1}$.