Hidden domain boundary dynamics toward crystalline perfection.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nonlinear Dynamics

Background:

• Understanding heterogeneity and disorder is crucial in nonequilibrium physics, affecting glasses and active matter.
• Probing microscopic trajectories, fluctuations, and entropy growth is key to analyzing irreversible processes.
• Model systems can illuminate general nonequilibrium phenomena and inform information processing technologies.

Purpose of the Study:

• To resolve nonequilibrium, heterogeneous, and irreversible mesoscale dynamics during a light-induced phase transition.
• To investigate nucleation, defect formation, and annihilation in ferroelectric superlattices.
• To understand the timescales and mechanisms governing these complex dynamics.

Main Methods:

• Application of ultrafast single-shot X-ray photon correlation spectroscopy (XPCS).
• Study of a tunable (PbTiO3)16/(SrTiO3)16 ferroelectric superlattice.
• Analysis of mesoscale dynamics, including phase transition nucleation and defect evolution.

Main Results:

• Captured the nucleation of a light-induced phase and the formation/annihilation of transient mesoscale defects.
• Identified a nonequilibrium correlation response spanning over 10 orders of magnitude in timescales.
• Observed multistep relaxation behavior and time-dependent long-time correlations explained by stochastic, non-Markovian domain wall dynamics.

Conclusions:

• Ferroelectric superlattices serve as a platform for studying tunable phase transitions and topological dynamics.
• XPCS can resolve complex dynamics, including defect evolution, in heterogeneous nonequilibrium systems.
• The findings provide a framework for probing correlated dynamics in disordered media and offer insights into energy/speed limits in information processing.