Suppression of transport in non-disordered quantum spin chains due to confined excitations

TL;DR

This paper demonstrates that confinement of quasi-particles in quantum spin chains can suppress transport, leading to non-thermalizing dynamics even without disorder, through numerical and analytical methods.

Contribution

It reveals that confinement effects can inhibit transport in homogeneous quantum systems, expanding understanding beyond disorder-induced localization.

Findings

Transport suppression observed in quantum Ising chains with confinement.

Numerical simulations agree with analytical models across regimes.

Atypical eigenstates linked to transport suppression and ETH violation.

Abstract

The laws of thermodynamics require any initial macroscopic inhomogeneity in extended many-body systems to be smoothed out by the time evolution through the activation of transport processes. In generic, non-integrable quantum systems, transport is expected to be governed by a diffusion law, whereas a sufficiently strong quenched disorder can suppress it completely due to many-body localization of quantum excitations. Here we show that the confinement of quasi-particles can also lead to transport suppression even if the dynamics are generated by homogeneous Hamiltonians. We demonstrate this in the quantum Ising chain with transverse and longitudinal magnetic fields in the paradigmatic case of the evolution of domain-wall states. We perform extensive numerical simulations of the dynamics which turn out to be in excellent agreement with an effective analytical description valid within both weak and strong confinement regimes. Our results show that the energy flow from "hot" to "cold" regions of the chain is suppressed for all accessible times. We argue that this phenomenon is connected with the presence of atypical states in the many-body energy spectrum which violate the eigenstate thermalization hypothesis, as recently reported in the literature.