Kovacs Effect in a Fragile Glass Model

TL;DR

This paper demonstrates the Kovacs effect, a non-monotonic relaxation phenomenon, in an exactly solvable dynamical model with interacting fast and slow modes, mimicking behaviors seen in polymers, granular materials, and molecular liquids.

Contribution

It introduces a solvable model that reproduces the Kovacs effect, providing insights into its origin in systems with coupled fast and slow dynamics.

Findings

The model exhibits the Kovacs effect under temperature shift protocols.

Reproduces non-monotonic relaxation similar to experimental observations.

Applicable to polymers, granular materials, and molecular liquids.

Abstract

The Kovacs protocol, based on the temperature shift experiment originally conceived by A.J. Kovacs for glassy polymers, is implemented in an exactly solvable dynamical model. This model is characterized by interacting fast and slow modes represented respectively by spherical spins and harmonic oscillator variables. Due to this fundamental property, the model reproduces the characteristic non-monotonic evolution known as the ``Kovacs effect'', observed in polymers, in granular materials and models of molecular liquids, when similar experimental protocols are implemented.