# Entanglement of condensed magnons via momentum-space fragmentation

## TL;DR

This paper proposes a method to engineer and detect momentum-space entanglement in magnon condensates within frustrated antiferromagnets, revealing quantum critical behavior and accessible experimental signatures.

## Contribution

It introduces a scheme to generate and measure momentum-space entanglement in magnon condensates near quantum critical points in frustrated antiferromagnets.

## Key findings

- Entanglement entropy shows singularity at quantum critical point
- Momentum-space entanglement can be observed via magnetic structure factor
- Model applicable to real materials and quantum simulators

## Abstract

A scheme is presented for engineering momentum-space entanglement of fragmented magnon condensates. We consider easy plane frustrated antiferromagnets in which the magnon dispersion has degenerate minima that represent umbrella chiral spin textures. With an applied magnetic field, we tune the Hamiltonian near a quantum critical point that is is signaled by a singularity in the entanglement entropy. The ground state develops momentum-space entanglement of the chiral spin textures. The size of the entangled superposition is accessible experimentally through the magnetic structure factor. Our model is motivated by equilibrium magnon condensates in frustrated antiferromagnets such as CsCuCl3, and it can also be simulated in spin-orbit coupled Mott insulators in atomic optical lattices and circuit quantum electrodynamics.