Thermal bistability in laser-cooled trapped ions

TL;DR

This paper investigates the nonlinear temperature bistability in large ion clouds trapped and laser-cooled, highlighting how oscillating field amplitude and ion density influence heating rates and state switching.

Contribution

It introduces a numerical simulation approach to analyze how rf field amplitude and ion number affect temperature bistability in laser-cooled ion clouds.

Findings

Heating rate is largely independent of ion number.

Oscillating field amplitude strongly influences heating.

Bistability can be used to detect perturbations.

Abstract

The non-linear dynamics of large ion clouds ($N \geq 256 $ ions) trapped in radio-frequency traps and coupled to laser-cooling give rise to a bistable behaviour of the temperature. Numerical simulations of the free evolution of a large three-dimensional spherical cloud is used to characterise how the oscillating field amplitude and the ion number control the rf heating rate and the switching between the two stable states. We show that the heating rate does not significantly depends on the ion number but strongly depends on the oscillating field. This exhibits the major role played by the density of the ensemble. The competition between the radio-frequency heating and the laser cooling is also discussed. They are used to design scenarii to take advantage of the threshold effect to detect and quantify perturbations by an intruder.