  Liquids crystallize as they cool; however, when crystallization is avoided in
some way, they supercool, maintaining their liquidity, and freezing into glass
at low temperatures, as ubiquitously observed. These metastable states
crystallize over time through the classical dynamics of nucleation and growth.
However, it was recently found that Coulomb interacting electrons on
charge-frustrated triangular lattices exhibit supercooled liquid and glass with
quantum nature and they crystallize, raising fundamental issues : what features
are universal to crystallization at large and specific to that of quantum
systems? Here, we report our experimental challenges that address this issue
through the spatiotemporal observation of electronic crystallization in an
organic material. With Raman microspectroscopy, we are the first to
successfully perform real-space and real-time imaging of electronic
crystallization. The results directly capture strongly temperature-dependent
crystallization profiles indicating that nucleation and growth proceed at
distinctive temperature-dependent rates, which is common to conventional
crystallization. Remarkably, however, the growth rate is many orders of
magnitude larger than that in the conventional case, which is attributable to
the quantum effect. The temperature characteristics of nucleation and growth
are universal, whereas unusually fast growth kinetics features quantum
crystallization where a quantum-to-classical catastrophe occurs in interacting
electrons.
