  We investigate the role of phase transitions into the spontaneous emission
rate of quantum emitters embedded in a critical medium. Using a Landau-Ginzburg
approach, we find that, in the broken symmetry phase, the emission rate is
reduced or even suppressed due to the photon mass generated by the Higgs
mechanism. Moreover, we show that the spontaneous emission presents a
remarkable dependence upon the critical exponents associated to a given phase
transition, allowing for an optical determination of the universality class.
Our findings not only demonstrate that the Purcell effect constitutes an
efficient optical probe of distinct critical phenomena, but they also unveil
that a more general connection between phase transitions and spontaneous
emission exist, as previous experimental and numerical evidences suggest.
