Task Progress:
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The FY2020 and FY2021 periods of this work were centrally focused on data collection from the CAL instrument, which began collection of ultracold-shell data in December 2018 and throughout 2019. Lundblad and postdoctoral associates Ryan Carollo and Joseph Murphree were central drivers of this work in this period, together with our partner at Jet Propulsion Laboratory (JPL), David Aveline, who in addition to service as co-investigator was our primary liaison to experimental operations. Theory co-investigators Smitha Vishveshwara and Courtney Lannert provided helpful insight and critical support, especially in regard to computational modeling of observed phenomena.
Phase 1 ("SM2") of the operation continued until the end of calendar 2019. Our datasets from this period focus on the generation of ultracold shell systems, confirming theoretical predictions that microgravity would enable their occurrence. We performed thermometry on the resulting shells as a function of size, and also explored the wide variety of shell sizes that could be created with this protocol. Reduction and analysis of this data is in process. A key conclusion of this work appears to be that while ultracold shells are possible in microgravity, maintaining the BEC state across the inflation process is difficult, due to nonadiabiaticity and low initial condensate fraction. Nevertheless, these observations represent physics impossible (or prohibitively difficult) to observe in a terrestrial setting, and have opened a new pathway in ultracold atomic physics research enabled by CAL and the International Space Station (ISS).
Phase 2 ("SM3") of the CAL operation commenced soon after and is ongoing. With a new atom chip geometry, SM3 permits us to explore shells with more spherical aspect ratios and possessing reduced inhomogeneity due to a larger rf coil. We have explored the parameter space of shell geometry and temperature with several different trap configurations, and we have also initiated an effort to use CAL's atom-interferometer Bragg beam to probe the nature of these ultracold shells. Looking ahead to upcoming upgrades, we hope to apply a second rf/microwave field in order to evaporatively cool the samples in the shell, thereby avoiding the heating associated with shell inflation; we also hope to use an additional signal associated with an upcoming upgrade to perform rf/microwave spectroscopy of the shell state in order to better understand the nature of Bose–Einstein condensation in a shell geometry.
Continued theoretical development occurred within the shell collaboration, leading to published work from Padavic et al. focusing on potential vortex physics in ultracold shells. Lundblad also continued collaborative discussions with Dr. Barry Garraway of Sussex regarding the potential to use microwave fields aboard CAL to enhance bubble quality.
Many years of modeling effort from students and postdocs culminated in a paper presenting the idea of the shell project and realistic modeling of its experimental sequences ( https://doi.org/10.1038/s41526-019-0087-y ; see also Bibliography section). This paper is proving to be a useful resource for theorists around the world seeking to obtain a sense of the capabilities of CAL in the shell-physics context.
Results of our research activities were presented at several conferences, including the 2019 and 2020 American Physical Society (APS) Meetings of the Division of Atomic, Molecular, and Optical Physics (DAMOP). Additionally, Lundblad traveled to the December 2019 workshop in Ulm, Germany, focusing on the development of a successor instrument to CAL (Bose-Einstein Condensate and Cold Atom Laboratory (BECCAL)), and presented preliminary data.
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Abstracts for Journals and Proceedings
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Lundblad N, Carollo RA, Aveline DC, Lannert C, Padavic K, Rhyno B, Vishveshwara S. "Observations of ultracold atoms in microgravity shell potentials." 51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics, Portland, Oregon, June 1–5, 2020. Bulletin of the American Physical Society. 2020;65(4):Abstract: E01.00106. https://meetings.aps.org/Meeting/DAMOP20/Session/E01.106 , Jun-2020
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Abstracts for Journals and Proceedings
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Rhyno B, Padavic K, Sun K, Lannert C, Lundblad N, Vishveshwara S. "Thermodynamics and vortex physics in shell-shaped Bose-Einstein condensates." 51st Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics, Portland, Oregon, June 1–5, 2020. Bulletin of the American Physical Society. 2020 Jun;65(4):Abstract: Q01.00167. https://meetings.aps.org/Meeting/DAMOP20/Session/Q01.167 , Jun-2020
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Abstracts for Journals and Proceedings
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Padavic K, Sun K, Lannert C, Vishveshwara S. "Vortex Physics in Hollow Bose-Einstein Condensates." 50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics, Milwaukee, Wisconsin, May 27–31, 2019. Bulletin of the American Physical Society. 2019 May;64(4):Abstract: E01.00121. http://meetings.aps.org/Meeting/DAMOP19/Session/E01.121 , May-2019
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Abstracts for Journals and Proceedings
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Carollo RA, Gold M, Jiang X, Padavic K, Vishveshwara S, Lannert C, Aveline D, Lundblad N. "Shell-Geometry Bose-Einstein Condensates in Microgravity." 50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics, Milwaukee, Wisconsin, May 27–31, 2019. Bulletin of the American Physical Society. 2019 May;64(4):Abstract: E01.00131. http://meetings.aps.org/Meeting/DAMOP19/Session/E01.131 , May-2019
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Articles in Peer-reviewed Journals
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Lundblad N, Carollo RA, Lannert C, Gold MJ, Jiang X, Paseltiner D, Sergay N, Aveline DC. "Shell potentials for microgravity Bose-Einstein condensates." npj Microgravity. 2019 Dec 4;5:30. https://doi.org/10.1038/s41526-019-0087-y ; PMID: 31815180; PMCID: PMC6892894 , Dec-2019
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Articles in Peer-reviewed Journals
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Padavic K., Sun K, Lannert C, Vishveshwara S. "Vortex-antivortex physics in shell-shaped Bose-Einstein condensates." Physical Review A - Atomic, Molecular, and Optical Physics. 2020 Oct;102(4):043305. https://doi.org/10.1103/PhysRevA.102.043305 , Oct-2020
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Dissertations and Theses
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Padavic-Callaghan K. (Karmela Padavic-Callaghan) "Hollow condensates, topological ladders and quasiperiodic chains." Dissertation, University of Illinois, Urbana-Champaign, July 2020. , Jul-2020
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