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研究了非谐振势中超流Fermi气体的集体激发. 基于一维超流流体动力学模型, 采用变分法获得了体系从分子Bose-Einstein凝聚端渡越到Cooper对凝聚端时系统的两个低能激发模, 即偶极模和呼吸模. 分析发现: 在整个跨越区偶极模和呼吸模都发生了频移现象, 且在BCS端频移更加显著. 进一步研究发现在不同驱动振幅激发下超流Fermi气体质量中心和宽度变化呈现出了复杂动力学特性, 由于非谐振势的贡献,超流Fermi气体两低能模发生耦合, 使宽度变化产生量子拍频现象, 且拍频频率随着驱动振幅的增加而增大. 这种非线性耦合对外部驱动的响应在幺正区尤其显著.The collective excitations of a one-dimensional superfluid Fermi gas in an anharmonic trap are investigated. By using the variational approach, the frequency shifts about the dipole mode of the center-of-mass variations and the breathing mode of width variations are derived. It is found that the frequency shift in a unitary region is more significant. Under the excitations of different driving amplitudes, the two low-energy modes are coupled due to the contribution of the quartic item, and the quantum beating phenomenon comes into being. The frequency of beating increases with the driving amplitude. The dynamics of the width exhibits complex characteristics, especially, in the unitary region.
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Keywords:
- superfluid Fermi gas /
- anharmonic potential /
- collective excitations
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[1] Hara K M, Hemmer S L, Gehm M E 2002 Science 298 5601
[2] Loftus T, Regsl C A, Ticknor C 2002 Phys. Rev. Lett. 88 173201
[3] Greiner M 2003 Nature 426 537
[4] Regal C A, Greiner M, Jin D S 2004 Phys. Rev. Lett. 92 040403
[5] Zhao X D, Xie Z W, Zhang W P 2007 Acta Phys. Sin. 56 6358 (in Chinese) [赵兴东, 些征微, 张卫平 2007 物理学报 56 6358]
[6] Ma Y, Fu L B, Yang Z A, Liu J 2006 Acta Phys. Sin. 55 5623 (in Chinese) [马云, 傅立斌, 杨志安, 刘杰 2006 物理学报 55 5623]
[7] Zhou L, Kong L B, Zhan M S 2008 Chin. Phys. B 17 1601
[8] Wang G F, Liu B, Fu L B, Zhao H 2007 Acta Phys. Sin. 56 3733 (in Chinese) [王冠芳, 刘彬, 傅立斌, 赵鸿 2007 物理学报 56 3733]
[9] Chin J K 2006 Nature 443 961
[10] Rodriguez M, Tòrma P 2004 Phys. Rev. A 69(R) 041602
[11] Zhai H, Ho T L 2007 Phys. Rev. Lett. 99 10042
[12] Moon E G, Nikolić P, Sachdev S 2007 Phys. Rev. Lett. 99 230403
[13] Pitaevskii L P, Stringari S, Orso G 2005 Phys. Rev. A 71 053602
[14] Kim Y E, Zubarev A L 2004 Phys. Rev. A 70 033612
[15] Manini N , Salasnich L 2005 Phys. Rev. A 71 033625
[16] Wen W, Zhou Y, Huang G X 2008 Phys. Rev. A 77 033623
[17] Wen W, Shen S Q, Huang G X 2010 Phys. Rev. B 81 014528
[18] Dong H, Ma Y L 2009 Chin. Phys. B 18 715
[19] Chin C, Bartenstein M, Altmeyer A 2004 Science 305 5687
[20] Li G Q, Fu L B, Xue J K, Chen X Z, Liu J 2006 Phys. Rev. A 74 055601
[21] Jin D S, Ensher J R, Matthews M R 1996 Phys. Rev. Lett. 77 420423
[22] Zhang A X, Xue J K 2009 Phys. Rev. A 80 043617
[23] Xue J K, Zhang A X 2008 Phys. Rev. Lett. 101 180401
[24] Wu Y, Yang X 2007 Phys. Rev. A 76 013832
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