Inherent-State Melting and the Onset of Glassy Dynamics in Two-Dimensional Supercooled Liquids

Below the onset temperature T_o, most glass formers are characterized by the super-Arrhenius temperature dependence of their equilibrium relaxation time. In this supercooled regime, the relaxation dynamics also proceeds through localized elastic excitations [1] corresponding to hopping events between inherent states. Despite its importance in distinguishing the supercooled regime from the high-temperature regime, the microscopic origin of T_o is not yet known. Here, we construct a theory for the onset temperature in two dimensions [2] and find that a binding-unbinding transition of dipolar elastic excitations, analogous to the Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory, describes the transition from the supercooled regime to the high-temperature one. The predicted transition temperature agrees with the onset temperature found in various two-dimensional (2D) atomistic models of glass formers and an experimental binary colloidal system confined to a water-air interface [3]. We further find the predictions for the renormalized elastic moduli to agree with the experimentally observed values below T_o for the latter 2D colloidal system.



[1] Hasyim, Mandadapu, J. Chem. Phys. 155 (4), 44504, (2021)

[2] Fraggedakis, Hasyim, Mandadapu, arXiv:2204.07528, (2022)

[3] Klix, Maret, Keim, Physical Review X 5.4 (2015)