Journal of Low Temperature Physics

, Volume 187, Issue 5–6, pp 668–676 | Cite as

Pseudogap Phenomena Near the BKT Transition of a Two-Dimensional Ultracold Fermi Gas in the Crossover Region



We investigate strong-coupling properties of a two-dimensional ultracold Fermi gas in the normal phase. In the three-dimensional case, it has been shown that the so-called pseudogap phenomena can be well described by a (non-self-consistent) T-matrix approximation (TMA). In the two-dimensional case, while this strong-coupling theory can explain the pseudogap phenomenon in the strong-coupling regime, it unphysically gives large pseudogap size in the crossover region, as well as in the weak-coupling regime. We show that this difficulty can be overcome when one improves TMA to include higher-order pairing fluctuations within the framework of a self-consistent T-matrix approximation (SCTMA). The essence of this improvement is also explained. Since the observation of the BKT transition has recently been reported in a two-dimensional \(^6\hbox {Li}\) Fermi gas, our results would be useful for the study of strong-coupling physics associated with this quasi-long-range order.


Ultracold Fermi gas Two-dimensional system BKT phase transition 



We thank H. Tajima, T. Yamaguchi, P. van Wyk , and D. Kagamihara for discussions. M. M. was supported by Graduate School Doctoral Student Aid Program from Keio University. R. H. was supported by a Grant-in-Aid for JSPS fellows. D. I. was supported by Grant-in-Aid for Young Scientists (B) (No. 16K17773) from JSPS in Japan. This work was supported by the KiPAS project in Keio university. Y.O was supported by Grant-in-Aid for Scientific Research from MEXT and JSPS in Japan (Nos. 15K00178, 15H00840, 16K05503).


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Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  1. 1.Faculty of Science and TechnologyKeio UniversityYokohamaJapan

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