BCS pairing state in an asymmetric binary Bose gas

doi:10.1088/1674-1056/ae0160

中国物理B ›› 2026, Vol. 35 ›› Issue (4): 46701-046701.doi: 10.1088/1674-1056/ae0160

BCS pairing state in an asymmetric binary Bose gas

Zesheng Shen(沈泽盛) and Lan Yin(尹澜)†

School of Physics, Peking University, Beijing 100871, China

收稿日期:2025-05-16 修回日期:2025-08-26 接受日期:2025-09-02 发布日期:2026-04-13
通讯作者: Lan Yin E-mail:yinlan@pku.edu.cn

BCS pairing state in an asymmetric binary Bose gas

Zesheng Shen(沈泽盛) and Lan Yin(尹澜)†

School of Physics, Peking University, Beijing 100871, China

Received:2025-05-16 Revised:2025-08-26 Accepted:2025-09-02 Published:2026-04-13
Contact: Lan Yin E-mail:yinlan@pku.edu.cn

摘要/Abstract

摘要： The BCS pairing state has been predicted to be stable in a symmetric binary Bose gas with the intraspecies repulsion and interspecies attraction. In experiments, the binary Bose gases are generally asymmetric. In this work, we study the pairing state in a dilute asymmetric binary Bose system with the intraspecies repulsions and interspecies attraction and show that it is stable in a certain region of the phase space. We find that there always exists a best density ratio for given total density and coupling constants, where the temperature width of the BCS region is maximized. At the best density ratio, both components have the almost same ideal BEC temperature. We also found that there are two critical density ratios where the BCS phase vanishes. The stability of the BCS state against pairing fluctuations is shown by expanding the Helmholtz free energy of BCS state near the normal state and proving that it is a local minimum point.

关键词: pairing states, Bose-Einstein condensates

Abstract: The BCS pairing state has been predicted to be stable in a symmetric binary Bose gas with the intraspecies repulsion and interspecies attraction. In experiments, the binary Bose gases are generally asymmetric. In this work, we study the pairing state in a dilute asymmetric binary Bose system with the intraspecies repulsions and interspecies attraction and show that it is stable in a certain region of the phase space. We find that there always exists a best density ratio for given total density and coupling constants, where the temperature width of the BCS region is maximized. At the best density ratio, both components have the almost same ideal BEC temperature. We also found that there are two critical density ratios where the BCS phase vanishes. The stability of the BCS state against pairing fluctuations is shown by expanding the Helmholtz free energy of BCS state near the normal state and proving that it is a local minimum point.

Key words: pairing states, Bose-Einstein condensates

中图分类号: (Ultracold gases, trapped gases)

67.85.-d

03.75.Hh (Static properties of condensates; thermodynamical, statistical, and structural properties)

Zesheng Shen(沈泽盛) and Lan Yin(尹澜). BCS pairing state in an asymmetric binary Bose gas[J]. 中国物理B, 2026, 35(4): 46701-046701.

Zesheng Shen(沈泽盛) and Lan Yin(尹澜). BCS pairing state in an asymmetric binary Bose gas[J]. Chin. Phys. B, 2026, 35(4): 46701-046701.

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BCS pairing state in an asymmetric binary Bose gas

BCS pairing state in an asymmetric binary Bose gas

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