Spin glasses, the quantum annealing, colloidal glasses and crystals: exploring complex free-energy landscapes

Abstract

Glassy behavior is one of the main open problems in condensed matter physics. In this thesis, we approach the problem by studying spin-glasses and colloids, using several complementary strategies. From the point of view of model building, we propose a new model, the hypercube model, which is mean-field but defined in a metric space. We show that, also in Mean Field, the spin-glass non-equilibrium dynamics is a domain-growth process very similar to its three-dimensional counterpart. We also consider spin-glasses in three spatial dimensions, focusing on temperature chaos. Thanks to the low-temperature configurations equilibrated with Janus, we show that temperature chaos can be aptly described through a large-deviations functional. The finite-size scaling behavior can be predicted in details from this functional, including the pre-asymptotic regime where chaos is driven by rare events. We also address the problem of finding new, efficient algorithms to study glassy systems. In particular, in the context of the Quantum-Adiabatic algorithm we discuss strategies for bypassing the "first-order bottleneck". Our approach is successfully put to work on the p-spin ferromagnetic model. We also show how to use tethered Monte Carlo (a recent refinement of Umbrella Sampling) to handle problems with more than one order parameter, such as hard-spheres crystallization. We study the crystallization transition equilibrating the largest systems to date, and obtaining very accurate determinations of the coexistence pressure and the interfacial free-energy. We also show our efforts to characterize the solid phase in a system of soft spheres at very high polydispersity.