Dynamic signature of the thermodynamic transition in a novel mean field system

TL;DR

This study introduces a mean field model with pseudo neighbours that reveals a clear dynamical signature of the thermodynamic transition, linking persistent pseudo bonds to the configurational entropy vanishing point.

Contribution

It demonstrates how pseudo bonds in a mean field system serve as a dynamical indicator of the thermodynamic transition, establishing a new connection between bond persistence and entropy.

Findings

Pseudo bonds are long-lived and temperature-dependent.

Number of surviving pseudo bonds correlates with the thermodynamic transition temperature T_K.

Breakdown of the Adam Gibbs relation at high temperatures.

Abstract

Understanding the connection between thermodynamics and dynamics in glass-forming liquids remains a central challenge in condensed matter physics. In this study, we investigate a novel model system that enables a continuous crossover from a standard three dimensional liquid to a fully connected mean field like system by introducing pseudo neighbours. These pseudo neighbours enhance the effective connectivity of the system without altering its local structure. While their presence slows down the dynamics, they influence thermodynamic properties even more significantly. In particular, the configurational entropy obtained via thermodynamic integration vanishes at a temperature much higher than the temperature where the dynamics begin to slow down, leading to a clear breakdown of the Adam Gibbs relation. To uncover a possible dynamical signature of this thermodynamic transition, we analyse bond breakage dynamics. Unlike real-real bonds, which decay similarly in both the parent Kob Andersen model and its mean field variant, real-pseudo bonds exhibit long lived, persistent behaviour with strong temperature dependence. These bonds do not fully decay over time, leading to a finite saturation value of the bond breakage correlation function. Remarkably, we show that the number of surviving pseudo bonds can be analytically estimated and correlates directly with the thermodynamic transition temperature T_K. We propose a phenomenological relation between T_K and the number of surviving pseudo-bonds, establishing a novel link between thermodynamic and dynamic observables. Our results suggest that these persistent pseudo bonds serve as a robust dynamical signature of the thermodynamic transition, and the system might have properties analogous to those of randomly bonded ultrastable glasses.