--- _id: '1033' abstract: - lang: eng text: Systems of three interacting particles are notorious for their complex physical behaviour. A landmark theoretical result in few-body quantum physics is Efimov\'s prediction1,2 of a universal set of bound trimer states appearing for three identical bosons with a resonant two-body interaction. Counterintuitively, these states even exist in the absence of a corresponding two-body bound state. Since the formulation of Efimov\'s problem in the context of nuclear physics 35 years ago, it has attracted great interest in many areas of physics3-8. However, the observation of Efimov quantum states has remained an elusive goal3,5. Here we report the observation of an Efimov resonance in an ultracold gas of caesium atoms. The resonance occurs in the range of large negative two-body scattering lengths, arising from the coupling of three free atoms to an Efimov trimer. Experimentally, we observe its signature as a giant three-body recombination loss9,10 when the strength of the two-body interaction is varied. We also detect a minimum 9,11,12 in the recombination loss for positive scattering lengths, indicating destructive interference of decay pathways. Our results confirm central theoretical predictions of Efimov physics and represent a starting point with which to explore the universal properties of resonantly interacting few-body systems7. While Feshbach resonances13,14 have provided the key to control quantum-mechanical interactions on the two-body level, Efimov resonances connect ultracold matter15 to the world of few-body quantum phenomena. acknowledgement: "We thank E. Braaten, C. Greene, B. Esry, H. Hammer and T. Ko ̈hler for many discussions and E. Kneringer for support regarding the data analysis. We acknowledge support by the Austrian Science Fund (FWF) within Spezialforschungsbereich 15 and within the Lise Meitner programme, and by the\r\nEuropean Union in the frame of the TMR networks ‘Cold Molecules’ and ‘FASTNet’. M.M. is supported within the Doktorandenprogramm of the Austrian\r\nAcademy of Sciences." article_processing_charge: No author: - first_name: Tobias full_name: Kraemer, Tobias last_name: Kraemer - first_name: Michael full_name: Mark, Michael last_name: Mark - first_name: Philipp full_name: Waldburger, Philipp last_name: Waldburger - first_name: Johann G full_name: Danzl, Johann G id: 42EFD3B6-F248-11E8-B48F-1D18A9856A87 last_name: Danzl orcid: 0000-0001-8559-3973 - first_name: Cheng full_name: Chin, Cheng last_name: Chin - first_name: Bastian full_name: Engeser, Bastian last_name: Engeser - first_name: Adam full_name: Lange, Adam last_name: Lange - first_name: Karl full_name: Pilch, Karl last_name: Pilch - first_name: Antti full_name: Jaakkola, Antti last_name: Jaakkola - first_name: Hanns full_name: Nägerl, Hanns last_name: Nägerl - first_name: Rudolf full_name: Grimm, Rudolf last_name: Grimm citation: ama: Kraemer T, Mark M, Waldburger P, et al. Evidence for Efimov quantum states in an ultracold gas of caesium atoms. Nature. 2006;440(7082):315-318. doi:10.1038/nature04626 apa: Kraemer, T., Mark, M., Waldburger, P., Danzl, J. G., Chin, C., Engeser, B., … Grimm, R. (2006). Evidence for Efimov quantum states in an ultracold gas of caesium atoms. Nature. Nature Publishing Group. https://doi.org/10.1038/nature04626 chicago: Kraemer, Tobias, Michael Mark, Philipp Waldburger, Johann G Danzl, Cheng Chin, Bastian Engeser, Adam Lange, et al. “Evidence for Efimov Quantum States in an Ultracold Gas of Caesium Atoms.” Nature. Nature Publishing Group, 2006. https://doi.org/10.1038/nature04626. ieee: T. Kraemer et al., “Evidence for Efimov quantum states in an ultracold gas of caesium atoms,” Nature, vol. 440, no. 7082. Nature Publishing Group, pp. 315–318, 2006. ista: Kraemer T, Mark M, Waldburger P, Danzl JG, Chin C, Engeser B, Lange A, Pilch K, Jaakkola A, Nägerl H, Grimm R. 2006. Evidence for Efimov quantum states in an ultracold gas of caesium atoms. Nature. 440(7082), 315–318. mla: Kraemer, Tobias, et al. “Evidence for Efimov Quantum States in an Ultracold Gas of Caesium Atoms.” Nature, vol. 440, no. 7082, Nature Publishing Group, 2006, pp. 315–18, doi:10.1038/nature04626. short: T. Kraemer, M. Mark, P. Waldburger, J.G. Danzl, C. Chin, B. Engeser, A. Lange, K. Pilch, A. Jaakkola, H. Nägerl, R. Grimm, Nature 440 (2006) 315–318. date_created: 2018-12-11T11:49:47Z date_published: 2006-03-16T00:00:00Z date_updated: 2021-01-12T06:47:48Z day: '16' doi: 10.1038/nature04626 extern: '1' intvolume: ' 440' issue: '7082' language: - iso: eng main_file_link: - open_access: '1' url: https://arxiv.org/abs/cond-mat/0512394 month: '03' oa: 1 oa_version: None page: 315 - 318 publication: Nature publication_status: published publisher: Nature Publishing Group publist_id: '6356' status: public title: Evidence for Efimov quantum states in an ultracold gas of caesium atoms type: journal_article user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87 volume: 440 year: '2006' ...