Lee-Yang theory of Bose-Einstein condensation

Brange, Fredrik; Pyhäranta, Tuomas; Heinonen, Eppu; Brandner, Kay; Flindt, Christian

Abstract

Bose-Einstein condensation happens as a gas of bosons is cooled below its transition temperature, and the ground state becomes macroscopically occupied. The phase transition occurs in the thermodynamic limit of many particles. However, recent experimental progress has made it possible to assemble quantum many-body systems from the bottom up, for example, by adding single atoms to an optical lattice one at a time. Here, we show how one can predict the condensation temperature of a Bose gas from the energy fluctuations of a small number of bosons. To this end, we make use of recent advances in Lee-Yang theories of phase transitions, which allow us to determine the zeros and the poles of the partition function in the complex plane of the inverse temperature from the high cumulants of the energy fluctuations. By increasing the number of bosons in the trapping potential, we can predict the convergence point of the partition-function zeros in the thermodynamic limit, where they reach the inverse critical temperature on the real axis. Using fewer than 100 bosons, we can estimate the condensation temperature for a Bose gas in a harmonic potential in two and three dimensions, and we also find that there is no phase transition in one dimension as one would expect.

Citation

Brange, F., Pyhäranta, T., Heinonen, E., Brandner, K., & Flindt, C. (2023). Lee-Yang theory of Bose-Einstein condensation. Physical Review A, 107(3), Article 033324. https://doi.org/10.1103/physreva.107.033324

• Journal Article Type: Article
• Acceptance Date: Mar 1, 2023
• Online Publication Date: Mar 23, 2023
• Publication Date: 2023-03
• Deposit Date: May 1, 2023
• Publicly Available Date: May 10, 2023
• Journal: Physical Review A
• Print ISSN: 2469-9926
• Electronic ISSN: 2469-9934
• Publisher: American Physical Society (APS)
• Peer Reviewed: Peer Reviewed
• Volume: 107
• Issue: 3
• Article Number: 033324
• DOI: https://doi.org/10.1103/physreva.107.033324
• Keywords: Bose-Einstein condensates; phase transitions; Lee-Yang & Fisher zeroes
• Public URL: https://nottingham-repository.worktribe.com/output/19287107
• Publisher URL: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.107.033324