# Absence of Ergodicity without Quenched Disorder: from Quantum Disentangled Liquids to Many-Body Localization

## TL;DR

This paper demonstrates that many-body localization and complex entanglement structures can occur in disorder-free quantum systems, revealing new insights into ergodicity absence without quenched disorder.

## Contribution

It introduces models showing ergodicity breaking and many-body localization without quenched disorder, using duality mappings and exact solutions.

## Key findings

- Existence of quantum disentangled liquids with mixed entanglement scaling.
- Mapping to disordered XXZ spin chain confirms many-body localization.
- Disorder-free systems can exhibit logarithmic entanglement growth.

## Abstract

We study the time evolution after a quantum quench in a family of models whose degrees of freedom are fermions coupled to spins, where quenched disorder appears neither in the Hamiltonian parameters nor in the initial state. Focussing on the behaviour of entanglement, both spatial and between subsystems, we show that the model supports a state exhibiting combined area/volume law entanglement, being characteristic of the quantum disentangled liquid. This behaviour appears for one set of variables, which is related via a duality mapping to another set, where this structure is absent. Upon adding density interactions between the fermions, we identify an exact mapping to an XXZ spin-chain in a random binary magnetic field, thereby establishing the existence of many-body localization with its logarithmic entanglement growth in a fully disorder-free system.