Entanglement and reciprocal dynamics of the Barnett and Einstein-de Haas responses in a quantum spin-rotor model

Abstract:We study the reciprocal Barnett and Einstein--de Haas effects in an exactly solvable quantum spin--rotor model that conserves the total angular momentum. For a single spin-$1/2$, the model describes rotation-dependent spin polarization, coherent transfer of angular momentum between the spin and the rotor, and the accompanying spin--rotor entanglement. At a recoil-compensation point, all angular-momentum sectors become synchronized, allowing complete spin reversal and a one-quantum shift of an arbitrary rotor wave packet. We then extend the model to two spins coupled to the same rotor. The rotor can now mediate entanglement between two distinct spins rather than only becoming entangled with the spin itself. The singlet forms a dark state, while the triplet sector remains coupled to the mechanical motion. At a special parameter point, the rotor returns to its original dynamical branch and disentangles from the spins, leaving behind a maximally entangled two-spin state locally equivalent to a Bell state.

9 pages, 3 figures. Major revision with co-author Holger Fehske added

Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el)

arXiv:2604.23768 [quant-ph]

(or arXiv:2604.23768v2 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2604.23768 Focus to learn more arXiv-issued DOI via DataCite

arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website.

Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them.

Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs.