Impact of long-range interactions on phase transitions in spin-boson models

• Applicant: Professor Dr. Sebastian Slama
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 465199066

The planned research explores the collective interaction of ultracold Rubidium atoms inside a high-finesse optical ring cavity, in conjunction with Rydberg interactions. The interplay of these two effects - occurring on vastly different length scales – gives rise to intriguing many-body phenomena that we aim to engineer, characterize and study within this project. The atoms will be trapped in a tweezer array located within the cavity's mode volume, enabling precise control over their spacing and thus over the strength of Rydberg interactions. The coupling between atomic ground and Rydberg states is implemented via a two-photon-transition. A distinct feature of the experiment is that both light fields driving this two-photon excitation are resonantly enhanced by the cavity mode. On the lower transition, we reach the regime of high cooperativity with single atoms, while cavity enhancement on the upper transition enables extremely large Rabi frequencies on the order of hundreds of megahertz. Thanks to strong coupling on the lower transition, the excitation dynamics become dependent on the atoms’ spin states inside the cavity. We will exploit this feature to study how existing Rydberg excitations – via feedback through the cavity field– affect the excitation of subsequent atoms. The goal is to realize nonlocal collective Rydberg excitations via nonlocal facilitation in the cavity, and to exert precise control over the number of excitations. In addition, we will generate long-range interactions between atoms in their ground and Rydberg states, mediated by the cavity light field in the cavity and described by an XY model. This will allow us to transfer Rydberg excitations across large distances inside the cavity via flip-flop processes, which we will detect, investigate, and optimize.

• DFG Programme: Research Units
• Subproject of: FOR 5413: Long-range interacting Quantum Spin systems out of equilibrium: Experiment, Theory and Mathematics
• International Connection: Brazil
• Co-Investigator: Professorin Dr. Beatriz Olmos Sanchez
• Cooperation Partner: Professor Dr. Philippe Courteille