  The simultaneous ordering of different degrees of freedom in complex
materials undergoing spontaneous symmetry-breaking transitions often involves
intricate couplings that have remained elusive in phenomena as wide ranging as
stripe formation, unconventional superconductivity or colossal
magnetoresistance. Ultrafast optical, x-ray and electron pulses can elucidate
the microscopic interplay between these orders by probing the electronic and
lattice dynamics separately, but a simultaneous direct observation of multiple
orders on the femtosecond scale has been challenging. Here we show that
ultrabroadband terahertz pulses can simultaneously trace the ultrafast
evolution of coexisting lattice and electronic orders. For the example of a
charge-density-wave (CDW) in 1T-TiSe2, we demonstrate that two components of
the CDW order parameter - excitonic correlations and a periodic lattice
distortion (PLD) - respond very differently to 12-fs optical excitation. Even
when the excitonic order of the CDW is quenched, the PLD can persist in a
coherently excited state. This observation proves that excitonic correlations
are not the sole driving force of the CDW transition in 1T-TiSe2, and
exemplifies the sort of profound insight that disentangling strongly coupled
components of order parameters in the time domain may provide for the
understanding of a broad class of phase transitions.
