Ludovic Berthier (ESPCI)

Salle 523, couloir 12-13, 5è étage

Equilibrium phase transition between a fluid and an amorphous solid

When a liquid is cooled, it can form a glass: a mechanically rigid but structurally disordered solid. Experimentally, this transformation occurs when the system falls out of equilibrium and no longer explores all accessible configurations on experimental timescales. A central open question, dating back more than a century, is whether this dynamical arrest reflects an underlying equilibrium phase transition. While theory predicts such a transition in idealized models (with deep connections to spin glass physics), its existence in realistic finite-dimensional systems remains unsettled. I will review this problem and present numerical results for a two-dimensional glass-forming liquid. By combining complementary Monte Carlo techniques, we equilibrate the system down to zero temperature over a range of system sizes and directly measure its equilibrium thermodynamic and structural properties. These results provide evidence for an equilibrium phase transition between a fluid and an amorphous solid. I will conclude by discussing the implications and open questions raised by this finding.