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When does a Fermi puddle become a Fermi sea? Emergence of Pairing in Two-Dimensional Trapped Mesoscopic Fermi Gases
by Emma K. Laird, Brendan C. Mulkerin, Jia Wang, and Matthew J. Davis
Submission summary
| Authors (as registered SciPost users): | Emma Laird |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202408_00033v2 (pdf) |
| Date submitted: | 2024-10-31 05:06 |
| Submitted by: | Laird, Emma |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
Abstract
Pairing lies at the heart of superfluidity in fermionic systems. Motivated by recent experiments in mesoscopic Fermi gases, we study up to six fermionic atoms with equal masses and equal populations in two different spin states, confined in a quasi-two-dimensional harmonic trap. We couple a stochastic variational approach with the use of an explicitly correlated Gaussian basis set, which enables us to obtain highly accurate energies and structural properties. Utilising two-dimensional two-body scattering theory with a finite-range Gaussian interaction potential, we tune the effective range to model realistic quasi-two-dimensional scattering. We calculate the excitation spectrum, pair correlation function, and number of pairs as a function of increasing attractive interaction strength. For up to six fermions in the ground state, we find that opposite spin and momentum pairing is maximised well below the Fermi surface in momentum space. By contrast, corresponding experiments on twelve fermions have found that pairing is maximal at the Fermi surface and strongly suppressed beneath [M. Holten et al., Nature 606, 287-291 (2022)]. This suggests that the Fermi sea — which acts to suppress pairing at low momenta via Pauli blocking — emerges in the transition from six to twelve particles.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Author comments upon resubmission
Please find our resubmitted manuscript attached to this correspondence in PDF format. We have responded to each referee in detail below their respective reports. Edits to the manuscript are written in different coloured text so that they are immediately obvious: orange text is associated with our response to Referee Report #1, blue text is associated with our response to Referee Report #2, and any additional corrections not associated with either report are written in green text.
Thank you for your time and kind regards,
Emma (Laird)
List of changes
1. Middle initials have been included in the authors' names, where appropriate [page 1].
2. Suburbs have been included in the affiliation addresses [page 1].
3. In Sec. 2, the word "large" which appears in reference to the effective range has been changed to "non-negligible" [line 189].
4. To clarify the concept of the critical binding energy, we have edited/added five sentences throughout Sec. 3.1 [lines 252-253, 264-267, 267-269, 277-279, 284-285].
5. A new middle panel (b) has been added to Fig. 2 which shows the ground- and first-excited-state energies separately, and the figure caption has been reworked accordingly [page 8].
6. Two sentences have been edited/added in the first paragraph of Sec. 3.1 to reflect the change in Fig. 2 [lines 218-221 and 224-226].
7. To distinguish between the "paired fraction" and the "number of pairs", the phrase "paired fraction" in the Abstract has been replaced with "number of pairs" [page 1], Sec. 3.3 has been renamed from "Paired Fraction" to "Number of Pairs" [pages 1 and 15], and one sentence has been added to the caption of Fig. 6 [page 17].
8. To provide more information on our computational limitations in the BEC regime, footnote 8 has been edited [page 12], footnote 11 has been added [page 16], and one sentence has been added to Sec. 3.3 [lines 413-416].
9. To clarify what we mean by the "many-body limit", one sentence [lines 263-264] has been rewritten and a new footnote [7] has been added to Sec. 3.1, and three sentences [lines 423-428] have been rewritten in Sec. 3.3.
10. Four names have been added to the Acknowledgements section [lines 531-533].
11. An error has been corrected in Eq. (A.10) of Appendix A.
12. Some figures have been repositioned within the text after the above edits were made.