Spin-phase transition in an array of quantum rings controlled by cavity photons

TL;DR

This paper models a controllable spin-phase transition in a 2D array of quantum rings influenced by cavity photons, revealing how electron-photon interactions can switch or suppress magnetic ordering.

Contribution

It introduces a novel theoretical framework combining spin-density functional and configuration interaction methods to study photon-controlled spin transitions in quantum ring arrays.

Findings

Spin-phase transition can be controlled by photon energy and coupling strength.

Strong electron-photon interaction can suppress the spin-phase transition.

Dynamical fluctuations in spin configurations are observed under time-dependent excitation.

Abstract

We model a spin-phase transition in a two-dimensional square array, or a lateral superlattice, of quantum rings in an external perpendicular homogeneous magnetic field. The electron system is placed in a circular cylindrical far-infrared photon cavity with a single circularly symmetric photon mode. Our numerical results reveal that the spin ordering of the two-dimensional electron gas in each quantum ring can be influenced or controlled by the electron-photon coupling strength and the energy of the photons. The Coulomb interaction between the electrons is described by a spin-density functional approach, but the para- and the diamagnetic electron-photon interactions are modeled via a configuration interaction formalism in a truncated many-body Fock-space, which is updated in each iteration step of the density functional approach. In the absence of external electromagnetic pulses this spin-phase transition is replicated in the orbital magnetization of the rings. The spin-phase transition can be suppressed by a strong electron-photon interaction. In addition, fluctuations in the spin configuration are found in dynamical calculations, where the system is excited by a time-dependent scheme specially fit for emphasizing the diamagnetic electron-photon interaction.