Generic dynamical features and thermalisation of isolated many-body quantum systems

Derek K. K. Lee, Sam Genway, Andrew Fu Wah Ho

Leonardo Biagetti, Guillaume Cecile, Jacopo De Nardis

We consider a system of classical hard rods or billiard balls in one dimension, initially prepared in a Bragg-pulse state at a given temperature and subjected to external periodic fields. We show that at late times the system always thermalises in the thermodynamic limit via a 3-stages process characterised by: an early phase where the dynamics is well described by Euler hydrodynamics, a subsequent where a (weak) turbulent phase is observed and where hydrodynamic gradient expansion can be broken, and a final one where the gas thermalises according to a viscous hydrodynamics. As the hard rod gas shares the same large-scale hydrodynamics as other quantum and classical integrable systems, we expect these features to universally characterise all many-body integrable systems in generic external potentials.

Eduardo Jonathan Torres-Herrera, Marco Távora, Léa Ferreira dos Santos

Shane Dooley, Graham Kells

It has recently been established that quantum many-body scarring can prevent the thermalisation of some isolated quantum systems, starting from certain initial states. One of the first models to show this was the so-called PXP Hamiltonian, which was used to theoretically model an experiment on a chain of strongly interacting Rydberg atoms. A defining feature of the PXP Hamiltonian is a set of dynamical constraints that make certain states inaccessible to the dynamics. In this paper we construct a class of spin chain models that are parameterised by a discrete variable ℓ that controls the "strength" of a dynamical constraint. We show that by increasing ℓ the constraint becomes weaker, in the sense that fewer states are excluded from the dynamics. The PXP Hamiltonian is special case for ℓ=2. By weakening the constraint to ℓ≥4, however, we find a more extreme version of quantum scarring than in the PXP Hamiltonian, with the number of scar states growing exponentially in the system size.

Felix M. Izrailev

Marcos Rigol, Vanja Dunjko, Maxim Olshanii