Kovacs effect in solvable model glasses

TL;DR

This paper demonstrates the Kovacs effect, a non-monotonic relaxation phenomenon, in an exactly solvable model of glasses with interacting fast and slow modes, capturing key features observed in various glassy systems.

Contribution

It introduces a solvable model with facilitated dynamics that reproduces the Kovacs effect, providing insights into the underlying mechanisms of glassy relaxation.

Findings

The model exhibits the Kovacs effect under temperature shift protocols.

Reproduces non-monotonic evolution similar to experimental observations.

Applicable to polymers, spin glasses, and granular materials.

Abstract

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