Understanding interacting quantum system dynamics when they undergo a phase transition should provide a new insight of the first steps of the universe after the Big Bang.
Kibble and Zurek work concerning spontaneous symmetry breaking happening while a quantum system undergoes a second order phase transition predicts the appearance of topological defects that remain in the system after the transition. These defects could explain the actual universe structure. The main objective of the project will be to force ultracold atom systems across a second order phase transition, in this case across the Bose-Einstein condensation threshold. The system dynamics after the process will be investigated by looking at the excitations remaining in the system. A fine measurement of the topological defects density in the gas should allow to validate or not Kibble and Zurek models.
Cooling a sodium dilute gas relies on recent techniques that are well known nowadays. Combining lasers and magnetic fields it is possible to slow down, trap and cool down to temperatures close to the absolute zero sodium dilute gases containing a few hundred thousand particles. One of the particularities of the experimental setup that will be built at the beginning of the project is the use of an atom chip, golden microstructures on top of a semiconductor, to achieve magnetic microtraps with novel geometries, allowing to confront Kibble and Zurek theories to a large diversity of physics situations. Another originality of the setup is to integrate a microwave waveguide on the chip to allow for the first time the investigation of a microwave resonance, a.k.a. Fano-Feshbach resonance, which will permit the control of interatomic interactions. Finally using fluorescence imaging should allow to reach the sensitivity necessary to resolve the topological defects that represents the heart of the project.
After 18 months of work, the project is suffering huge delays due to administrative problems that were encountered during the refurbishing of the lab room. For a little more than a month, we have been able to start the building of the experimental setup. We hope that the design work we have been focused on waiting the end of the building work will pay off and lead us quickly to our first results.
Many perspectives can be expected from the project, as there is still a lot to do in order to investigate in depth interacting quantum system dynamics. The amplitude of the expected perspectives should be estimated more easily after the completion of the building of the experimental setup and obtaining the first results.
Up to now only an article concerning correlations of non-interacting Bose gases close to the Bose-Einstein condensation threshold have been written in the framework of a collaboration between Villetaneuse, Vienna and Brisbane. This work is not directly re
This project concerns the investigation of Kibble-Zurek mechanisms, which describe the appearance of topological defects during symmetry breaking phase transitions. Such processes have been originally introduced in the context of cosmology. They can be simulated using cold Bose gases brought close to the Bose-Einstein condensation threshold and submitted to a quench forcing the system through the phase transition. Investigating the subsequent dynamics of the gas is the main goal of this proposal. Within the project, Bose gases will be prepared in low dimensional traps. Working in such regimes is appealing because it generally uncovers novel physical regimes but also facilitates the direct comparison with theoretical models.
The experiments will be performed on a new experimental setup, which will be built at the beginning of the project. It will include an atom chip used to create magnetic microtraps for neutral atoms. The design of the chip will contain a microwave guide allowing the investigation of microwave-induced Fano-Feschbach resonances. These can be used to modify the scattering properties of the atoms. They have been recently predicted and will be used within the project to trigger the dynamics of the studied systems and explore strongly interacting regimes of Bose gases.
Monsieur Aurélien Perrin (UNIVERSITE DE PARIS XIII) – email@example.com
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
LPL UNIVERSITE DE PARIS XIII
Help of the ANR 450,000 euros
Beginning and duration of the scientific project: December 2011 - 36 Months