Atom-Cavity Systems

Undriven

Driven

Controlled emergence of phases of matter in strongly correlated systems through external driving has been instrumental not only in advancing our understanding of many-body physics but also in the search for new functionalities for future quantum technologies. For example, shining laser at a superconductor can let us see glimpses of superconductivity at room temperature!

Unfortunately, in most cases, the complexity of quantum many-body systems, especially those in solid-state platforms, poses a substantial challenge to the fundamental understanding of genuine non-equilibrium phenomena. It is then desirable to observe and characterize dynamical control and emergence of phases in a relatively simple platform, such as ultracold atomic systems, to better understand them at a microscopic level.

Ultracold atoms cooled down to temperatures below hundred nanokelvin are some of the coldest objects in the universe. We combine cold atom physics and quantum optics to further our understanding of many-body physics and the interaction between light and matter. Atom-cavity setups, owing to their high degree of tunability, are promising platforms to emulate other quantum many-body systems or to form new non-equilibrium phases.

In collaboration with experimentalists, we study a Bose-Einstein condensate of atoms placed inside a high finesse optical cavity. This atom-cavity system serves as an example of a light-matter system that can be described by a relatively simple model. We are particularly interested in controlling competing quantum phases in this system via periodic driving.

In addition to control of desired static properties, external driving can also lead to the emergence of genuine dynamical phases of matter without any equilibrium counterparts. An example of such a phase is a time crystal. Similar to how solid-state crystals break space-translation symmetry, a time crystal spontaneously breaks time-translation symmetry by exhibiting regular behaviour in time. We propose and observe time crystals in the atom-cavity system.

Publication Highlights

Observation of a continuous time crystal, P. Kongkhambut, J. Skulte, L. Mathey, J. G. Cosme, A. Hemmerich, H. Keßler, Science, (2022). [arXiv]

News articles and interviews:

"Researchers observe continuous time crystal" (Phys.org)

"A new kind of time crystal has been created and lasts 10 milliseconds" (NewScientist)

Observation of a dissipative time crystal, H. Keßler, P. Kongkhambut, C. Georges, L. Mathey, J. G. Cosme, A. Hemmerich, Physical Review Letters 127, 043602, (2021) [Editors' Suggestion]. [arXiv]

Commentary articles:

"Time crystals in Open Systems" by Z. Gong and M. Ueda

"Quantum time crystals open up" by P. Ball

News articles and interviews:

"The first experimental realization of a dissipative time crystal" (Phys.org)

"Zu verrückt, um falsch zu sein" (Die Zeit)

"Auf den Spuren von Raum und Zeit" (Forschung und Lehre)

Torus bifurcation of a dissipative time crystal, J. G. Cosme, P. Kongkhambut, A. Bölian, R. J. L. Tuquero, J. Skulte, L. Mathey, A. Hemmerich, H. Keßler, Physical Review Letters 134, 223601, (2025). [arXiv]
Observation of a phase transition from a continuous to a discrete time crystal, P. Kongkhambut, J. G. Cosme, J. Skulte, M. A. Moreno Armijos L. Mathey, A. Hemmerich, H. Keßler, Reports on Progress in Physics, (2024).
Condensate formation in a dark state of a driven atom-cavity system, J. Skulte, P. Kongkhambut, S. Rao, L. Mathey, H. Keßler, A. Hemmerich, J. G. Cosme, Physical Review Letters 130, 163603, (2023). [arXiv]
Realization of a periodically driven open three-level Dicke model, P. Kongkhambut, H. Keßler, J. Skulte, L. Mathey, J. G. Cosme, A. Hemmerich, Physical Review Letters 127, 253601, (2021). [arXiv]
Light-induced coherence in an atom-cavity system, Ch. Georges, J. G. Cosme, L. Mathey, A. Hemmerich, Physical Review Letters 121, 220405, (2018).
Dynamical Control of Order in a Cavity-BEC System, J. G. Cosme, Ch. Georges, A. Hemmerich, L. Mathey, Physical Review Letters 121, 153001, (2018).

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