Possible observation of parametrically amplified coherent phasons in   K0.3MoO3 using time-resolved extreme-ultraviolet ARPES
  We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) in the Extreme Ultraviolet (EUV) to measure the time- and momentum-dependent electronic structure of photo-excited K0.3MoO3. Prompt depletion of the Charge Density Wave (CDW) condensate launches coherent oscillations of the amplitude mode, observed as a 1.7-THz-frequency modulation of the bonding band position. In contrast, the anti-bonding band oscillates at about half this frequency. We attribute these oscillations to coherent excitation of phasons via parametric amplification of phase fluctuations. 
H. Y. Liu, I. Gierz, J. C. Petersen, S. Kaiser, A. Simoncig, A. L.   Cavalieri, C. Cacho, I. C. E. Turcu, E. Springate, F. F...
cond-mat.str-el cond-mat.supr-con