Determine whether phonons drive hidden-order evolution

Determine whether coherent phonons actively promote domain evolution or hexatic-state formation in quantum materials undergoing photoinduced competing-order transitions.

Background

The review describes ultrafast electron microscopy observations in which charge-density-wave suppression occurs alongside multiple coherent phonons and in which a transient hexatic-like structural state appears. These observations establish correlated structural dynamics but do not establish that the phonons are the causal drivers.

Resolving whether phonons actively promote domain evolution or the formation of the hexatic-like state would distinguish phonon-driven switching from phonons that merely report or modulate an independently initiated electronic or structural transition.

References

While precision-controlled UEM captures sub-100-fs suppression of the charge-density-wave (CDW) structure factor alongside these multiple-order phonons, it is critical to note that these observations establish coupled structural dynamics rather than strictly phonon-driven switching; whether the phonons actively promote domain evolution or hexatic state formation remains unresolved.

— Ultrafast Electron Microscopy: A Quantitative Platform for Nonequilibrium Materials Research  (2609.30084 - Flannigan et al., 24 Sep 2026) in Section 5.2, “Phonons as Reporters and Drivers of Hidden Order”