Strongly coupled quantum phonon fluid in a solvable model

Abstract

We study a model of a large number of strongly coupled phonons that can be viewed as a bosonic variant of the Sachdev-Ye-Kitaev model. We determine the phase diagram of the model which consists of a glass phase and a disordered phase, with a first-order phase transition separating them. We compute the specific heat of the disordered phase, with which we diagnose the high-temperature crossover to the classical limit. We further study the real-time dynamics of the disordered phase, where we identify three dynamical regimes as a function of temperature. Low temperatures are associated with a semiclassical regime, where the phonons can be described as long-lived normal modes. High temperatures are associated with the classical limit of the model. For a large region in parameter space, we identify an intermediate-temperatures regime, where the phonon lifetime is of the order of the Planckian time scale $\hslash /k_{B}T$.

Typos corrected, references added, discussion improved

References in corpus (5)

• Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics
• Theory of universal incoherent metallic transport
• Bosonic Tensor Models at Large $N$ and Small $\epsilon$
• Thermalization and Possible Signatures of Quantum Chaos in Complex Crystalline Materials
• A lower bound to the thermal diffusivity of insulators