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Numerical Simulation of Ion Crystals and Sympathetic Cooling

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Directeur de thèse /Supervisor : Martina Knoop
Coordonnées/Email and address : martina.knoop, Tel
Co-encadrant /Co-advisor : Jofre Pedregosa, jofre.pedregosa

Description du sujet /Abstract :
This thesis project proposes to use Molecular Dynamic Simulations (MDS) to study different phenomena involving laser cooled ions in radio-frequency traps.
Second order phase transitions and defect formation
Ion crystals can be described as systems with long-range, unscreened Coulomb interactions, perfectly suited to study equilibrium and out-of-equilibrium statistical mechanics. The morphology of laser cooled ion crystals obtained in quadrupole linear RF traps can be easily modified by changing the trapping parameters. The 1D  2D topological change in linear quadrupole RF traps, has been shown to correspond to a second order phase transition [1].
This project will look at the transition from 3D  2D, in which case wall-domains can appear, bearing similarities with the 2D crystals obtained using dust particles trapped in a RF Plasma [2], where the interaction potential is of Yukawa-type rather than Coulomb. In addition, recent [3] work demonstrates interesting applications for soliton studies by using 1 ring ion chain  2 ring ion chain transitions. Such systems can be obtained using multipole radio-frequency traps [4]. The project will use MDS to explore crystal configurations under realistic conditions to gain new insight in fundamental questions and explore the feasibility of an experiment.
Sympathetic cooling
Thanks to the low temperature and the well-controlled conditions of ions in RF – traps, these systems are unique for high resolution spectroscopy. However laser-cooling is only applicable to a limited number of ions. The technique known as Sympathetic Cooling (SC) allows to use laser cooled ions as a cold reservoir to cool down other species. In particular, the subject will be focussed at SC of Highly Charged Ions (HCI)), which is a very promising approach to open the door to high resolution spectroscopy to HCI and Dr. J. Pedregosa has
collaborated in a recent proof of concept experiment [5]. The student will use MDS to explore and gain insight in such process with the prospect to apply the method to more exotic species.
The student will have the opportunity to collaborate with the experiment at Max-Planck-
Institute in Heidelberg.
The present project will allow the PhD student to acquire a solid basis in an exciting physics
domain (ion traps, laser cooling, thermodynamics) as well as to extending his/her
programming skills as the candidate is expected to contribute to an existing code, written in
FORTRAN95/OpenMP and running in Intel Xeon Phi co-processors.
[1] S. Fishman, G. De Chiara, T. Calarco and G. Morigi, Physical Review B 77, 064111 (2008)
[2] L. Couëdel, et. al. Phys. Rev. Lett. 104, 195001
[3] H. Landa, A. Retzker, T. Schaetz and B. Reznik, Physical Review Letters 113, 053001 (2014)
[4] C. Champenois, M. Marciante, J. Pedregosa-Gutierrez, M. Houssin, M. Knoop and M.
Kajita ; Phys. Rev. A 81, 043410 (2010)
[5] L. Schmöger et al., Science 347, 1233-1236 (2015)