Structural transitions of ion strings in quantum potentials

TL;DR

This paper investigates how strong light-ion coupling in a cavity affects the stability and structural transitions of ion chains, revealing bistability, cooling effects, and entanglement of excitations near the zigzag transition.

Contribution

It demonstrates the influence of cavity-mediated light-ion interactions on ion chain stability, bistability, and entanglement, highlighting novel quantum effects in optomechanical systems.

Findings

Bistability between linear and zigzag ion configurations.

Cavity-enhanced cooling into specific chain configurations.

Entanglement of photonic and vibrational excitations at steady state.

Abstract

We analyse the stability and dynamics of an ion chain confined inside a high-finesse optical resonator. When the dipolar transition of the ions strongly couples to one cavity mode, the mechanical effects of light modify the chain properties close to a structural transition. We focus on the linear chain close to the zigzag instability and show that linear and zigzag arrays are bistable for certain strengths of the laser pumping the cavity. For these regimes the chain is cooled into one of the configurations by cavity-enhanced photon scattering. The excitations of these structures mix photonic and vibrational fluctuations, which can be entangled at steady state. These features are signalled by Fano-like resonances in the spectrum of light at the cavity output.