Quantum thermodynamics and laser cooling with Silicon vacancies in diamond

Conventional optical refrigeration methods induce anti-Stokes fluorescence by weakly driving an optical transition at resonance. The emitted photons are higher in energy than those absorbed from the pumping laser, with the energy difference accounted for by the absorption of phonons from the host medium. We propose an alternative method for laser cooling which uses strong coherent driving, and analyse this method in the case of the Silicon vacancy defect center in diamond. The protocol exploits the formation of laser dressed states, which we show leads to an increase in the cooling power and reduced sensitivity to pump wavelength, when compared with the conventional weak incoherent driving method. We use a Born-Markov master equation to solve for the steady state of the driven open system and use the method of full counting statistics to compute the cooling spectrum. Our results suggest this approach could be effective for laser cooling to temperatures on the order of 1K.  The protocol is not specific to the Silicon vacancy center, and sheds light on the role of coherence in laser cooling and in quantum thermal machines more generally.