2025-09-02 パデュー大学
＜関連情報＞
- https://www.purdue.edu/newsroom/2025/Q3/explaining-a-quantum-oddity-with-5-atoms/
- https://www.pnas.org/doi/10.1073/pnas.2503390122
- https://www.nature.com/articles/nphys1253
- https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.83.1751
同一ボゾンの五体再結合 Five-body recombination of identical bosons
Michael D. Higgins and Chris H. Greene
Proceedings of the National Academy of Sciences Published:April 25, 2025
DOI:https://doi.org/10.1073/pnas.2503390122
Significance
Deep in the quantum limit, the atoms in a trapped ultracold gas constantly collide with each other, mostly two at a time with no energy exchanged. When 3 or more atoms simultaneously collide, however, they sometimes exchange energy and form bound subsystems; such a collision is referred to as a recombination event, and it usually ejects all participating atoms from the trap. Under certain conditions, 3-body losses are resonantly enhanced and very fast, which have been extensively studied. A few cases are also known where 4-body losses are dominant. The present study develops the theory of 5-body recombination losses and predicts conditions where that is the dominant loss process in an ultracold atomic gas held close to absolute zero temperature.
Abstract
This work treats resonant collisions between five identical ultracold bosons in the framework of the adiabatic hyperspherical representation. The five-body recombination rate coefficient is quantified using a semiclassical description in conjunction with an analysis of the lowest five-body hyperspherical adiabatic potential curves in a scattering length regime with no universal weakly bound tetramers, trimers, or dimers. A comparison is made between these results and the only existing experimental measurement of five-body loss in an ultracold gas of bosonic cesium atoms and with the lone theoretical estimation of the loss rate. The recombination rate for the process B + B + B + B + B → B4 + B is also computed in a different regime of scattering lengths where there is one universal bound tetramer by implementing a few-channel quantum scattering calculation based on five-body hyperspherical potential curves and nonadiabatic couplings. Our calculations predict regions where five-body recombination can cause decay of the atom cloud in an ultracold gas that is even faster than 3-body and 4-body recombination, which can ideally be tested by using the current generation of box traps having nearly uniform density.
普遍的な四体現象の特徴とエフィモフ効果との関係 Signatures of universal four-body phenomena and their relation to the Efimov effect
J. von Stecher,J. P. D’Incao & Chris H. Greene
Nature Physics Published:26 April 2009
DOI:https://doi.org/10.1038/nphys1253
Abstract
The problem of three interacting quantal bodies, in its various guises, seems deceptively simple, but it has also provided striking surprises, such as the Efimov effect1,2, which was confirmed experimentally3 only more than 35 years after its initial prediction. The importance of understanding the three-body problem was magnified by the explosion of ultracold science following the formation of Bose–Einstein condensates in 1995 (ref. 4). For ultracold gases, three-body recombination (where B+B+B collide to form B2+B) was quickly recognized as the main loss process and connected5,6,7,8 with the Efimov effect in the ‘universal’ realm of very large atom–atom scattering lengths a. The problem of four interacting bodies challenges theory far more than the three-body quantal problem. Some key insights have been achieved in recent years9,10,11,12,13,14,15,16. Here, we present a major extension of our understanding of the four-body problem in the universal large-a regime. Our results support a previous conjecture10 that two resonantly bound four-body states are attached to every universal three-body Efimov resonance and they improve the calculated accuracy of their universal properties. A hitherto unanalysed feature found in ultracold-gas experiments3 supports this universal prediction, and it provides the first evidence of four-body recombination (where B+B+B+B form B3+B, B2+B+B or B2+B2).
超低温限界における三原子再結合 Recombination of Three Atoms in the Ultracold Limit
Chris H. Greene and James P. Burke, Jr.
Physical Review Letters Published: 30 August, 1999
DOI: https://doi.org/10.1103/PhysRevLett.83.1751
Abstract
We identify two qualitatively different mechanisms that control three-body recombination in a spin-polarized gas near zero temperature. A universal curve describes the recombination rate versus the two-body scattering length . It grows as 4 for large ||, with different mechanisms for <0 and >0. Our calculations document a previously established mechanism that causes 3 to grow rapidly as the two-body scattering length increases toward +∞, and a new tunneling mechanism that produces an even stronger enhancement of 3 as →−∞. The expectations based on these two mechanisms can be modified by quantum mechanical interference or resonance effects.
