  Signatures of photo-induced superconductivity have been reported in cuprate
materials subjected to a coherent phonon drive. A 'cold' superfluid was
extracted from the transient Terahertz conductivity and was seen to coexist
with 'hot' uncondensed quasi-particles, a hallmark of a driven-dissipative
system of which the interplay between coherent and incoherent responses are not
well understood. Here, time resolved spontaneous Raman scattering was used to
probe the lattice temperature in the photo-induced superconducting state of
YBa2Cu3O6.48. An increase in lattice temperature of approximately 80 K was
observed by measuring the time dependent Raman scattering intensity of an
undriven 'spectator' phonon mode. This is to be compared with an estimated
increase in quasi-particle temperatures of nearly 200 K. These temperature
changes provide quantitative information on the nature of the driven state and
its decay, and may provide a strategy to optimize this effect.
