Strong-coupling emergence of dark states in XX central spin models

TL;DR

This paper demonstrates that the XX central spin model remains integrable under arbitrary magnetic fields and reveals the emergence of dark states in strong coupling regimes, regardless of magnetic field orientation.

Contribution

It shows the persistence of integrability in the XX central spin model with any magnetic field orientation and uncovers the universal emergence of dark states under strong coupling.

Findings

Dark states can exist with in-plane magnetic fields in strong coupling regimes.

Integrability of the model is maintained with arbitrary magnetic field orientation.

Dark states are universal across various coupling distributions.

Abstract

It was recently shown that the XX central spin model is integrable in the presence of a magnetic field perpendicular to the plane in which the coupling exists. A large number of its eigenstates are such that the central spin is not correlated to the environmental spins it is coupled to. In this work, we first demonstrate that the XX-central spin model remains integrable in the presence of an arbitrarily oriented magnetic field. We then show that, provided the coupling is strong enough, dark states can actually be found even in the presence of an in-plane magnetic field. We finally provide a simple explanation of this result and demonstrate its universality for a variety of distinct distributions of the coupling of the central spin to the various bath spins.