Markovian master equation and thermodynamics of a two-level system in a strong laser field

The recently developed technique combining the weak-coupling limit with the Floquet formalism is applied to a model of a two-level atom driven by a strong laser field and weakly coupled to heat baths. First, the case of a single electromagnetic bath at zero temperature is discussed and the formula for resonance fluorescence is derived. The expression describes the well-known Mollow triplet, but its details differ from the standard ones based on additional simplifying assumptions. The second example describes the case of two thermal reservoirs: an electromagnetic one at finite temperature and the second dephasing one, which can be realized as a phononic or buffer gas reservoir. It is shown using the developed thermodynamical approach that the latter system can work in two regimes depending on the detuning sign: a heat pump transporting heat from the dephasing reservoir to an electromagnetic bath or heating both, always at the expense of work supplied by the laser field.

Figure 1

Power spectral density function (47) in a process of nonresonant fluorescence in vacuum ($\Omega =0.85$, $\Delta =0.01$, $g=0.075$). The chosen ratio $g/\Omega$ and the value of $\mathcal{A}$ are very high in comparison to known physical examples in order to make visible the asymmetry of the line shape.