Quantum Disentangled Liquids

TL;DR

This paper introduces the concept of Quantum Disentangled Liquids (QDL), a new phase where light particles in multi-component quantum fluids do not fully thermalize and remain localized, challenging traditional statistical mechanics assumptions.

Contribution

It formally defines the QDL phase, explores its properties, and discusses its potential realization in systems like water, highlighting a novel non-thermal quantum phase.

Findings

QDL exhibits area-law entanglement entropy for light particles.

Heavy particles are fully thermalized while light particles remain localized.

Potential realization in water with proton localization on oxygen ions.

Abstract

We propose and explore a new finite temperature phase of translationally invariant multi-component liquids which we call a "Quantum Disentangled Liquid" (QDL) phase. We contemplate the possibility that in fluids consisting of two (or more) species of indistinguishable quantum particles with a large mass ratio, the light particles might "localize" on the heavy particles. We give a precise, formal definition of this Quantum Disentangled Liquid phase in terms of the finite energy density many-particle wavefunctions. While the heavy particles are fully thermalized, for a typical fixed configuration of the heavy particles, the entanglement entropy of the light particles satisfies an area law; this implies that the light particles have not thermalized. Thus, in a QDL phase, thermal equilibration is incomplete, and the canonical assumptions of statistical mechanics are not fully operative. We explore the possibility of QDL in water, with the light proton degrees of freedom becoming "localized" on the oxygen ions. We do not presently know whether a local, generic Hamiltonian can have eigenstates of the QDL form, and if it can not, then the non-thermal behavior discussed here will exist as an interesting crossover phenomena at time scales that diverge as the ratio of the mass of the heavy to the light species also diverges.