  Phase transitions with lowering temperature is a manifestation of decreased
entropy and within the Landau theoretical framework these are accompanied by
the symmetry breaking. Whenever a symmetry is broken weakly or strongly, it
leaves its trail and the same may be captured indirectly using renormalization
of the quasi-particle excitations. Cr2Ge2Te6, a quasi-two-dimensional magnetic
material, provides a rich playground to probe dynamics of the quasi-particle
excitations as well as multiple phase transitions with lowering temperature
intimately linked with the lattice and spin degrees of freedom. Here, we report
in-depth inelastic light scattering measurements on single crystals of
Cr2Ge2Te6 as a function of temperature, from 6 K to 330 K, and polarization.
Our measurements reveal the long as well as short range ordering of the spins
below Tc (~ 60 K) and T* (~ 180 K), respectively; setting the stage for broken
rotational and time reversal symmetry, gauged via the distinct renormalization
of the phonon self-energy parameters along with the modes intensity. Our
measurements also uncovered an intriguing dependence of the interaction
strength between discrete state (phonon here) and the underlying continuum,
quantified using the Fano asymmetry parameter, as a function of the scattered
light polarization. Our results suggest the possibility of tuning the
interaction strength using controlled scattered light and symmetry in this 2D
magnet.
