Observation of photon-photon thermodynamic processes under negative optical temperature conditions

• 成果类型: Article
• 署名作者: Muniz, A. L. Marques; Wu, F. O.; Jung, P. S.; Khajavikhan, M.; Christodoulides, D. N.; Peschel, U.
• 署名单位: Friedrich Schiller University of Jena; State University System of Florida; University of Central Florida; Warsaw University of Technology; University of Southern California
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-13933
• DOI: 10.1126/science.ade6523
• 发表日期: 2023-03-10
• 页码: 1019-+
• 关键词: statistical-mechanics

摘要

Statistical mechanics demands that the temperature of a system is positive provided that its internal energy has no upper bound. Yet if this condition is not met, it is possible to attain negative temperatures for which higher-order energy states are thermodynamically favored. Although negative temperatures have been reported in spin and Bose-Hubbard settings as well as in quantum fluids, the observation of thermodynamic processes in this regime has thus far remained elusive. Here, we demonstrate isentropic expansion-compression and Joule expansion for negative optical temperatures, enabled by purely nonlinear photon-photon interactions in a thermodynamic microcanonical photonic system. Our photonic approach provides a platform for exploring new all-optical thermal engines and could have ramifications in other bosonic systems beyond optics, such as cold atoms and optomechanics.