Dresden 2026 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 60: Critical Phenomena and Phase Transitions
DY 60.7: Vortrag
Freitag, 13. März 2026, 11:15–11:30, ZEU/0114
Nucleation in the Vicinity of the Spinodal — •Sune Kühne and Marcus Müller — Universität Göttingen Institut für Theoretische Physik Friedrich-Hund-Platz 1 37077 Göttingen
Nucleation plays a central role in initiating phase separation across diverse soft-matter systems, from synthetic polymer blends to biomolecular condensates. Near the spinodal, Cahn-Hilliard nucleation theory (CHNT) predicts that the free-energy barrier vanishes while the size and material excess of the critical nucleus diverge. Forming a large cluster significantly delays nucleation even in the absence of a free-energy barrier in analogy to approaching the spinodal from the unstable region. Yet experiments consistently report a finite rate of phase separation even while crossing the spinodal, challenging the classical CHNT scenario. In this work, we investigate the onset of phase separation in the near-spinodal regime and reveal how thermal fluctuations qualitatively modify the nucleation pathway. Using Monte Carlo simulations, we show that fluctuations can locally and transiently push the system beyond the spinodal threshold, enabling the formation of nuclei on a finite length scale well below the system size. This mechanism produces finite nucleation times and naturally explains the experimentally observed smooth crossover from nucleation-dominated to spinodal-like dynamics. By analyzing the free-energy landscape as well as the structure and dynamics of the density fluctuations that eventually become critical, we identify the key physical principles governing phase selection in metastable mixtures.
Keywords: Nucleation; Phase separation; Monte Carlo; Metastability
