摘要We find that uniform Bose atomic gases with weak attraction can undergo a Bardeen–Cooper–Schrieffer (BCS) condensation below a critical temperature. In the BCS condensation state, bare atoms with opposite wave vectors are bound into pairs, and unpaired bare atoms are transformed into a new kind of quasi-particles, i.e. the dressed atoms. The atom-pair system is a condensate or a superfluid and the dressed-atom system is a normal fluid. The critical temperature and the effective mass of dressed atoms are derived analytically. The transition from the BCS condensation state to the normal state is a first-order phase transition.
Abstract：We find that uniform Bose atomic gases with weak attraction can undergo a Bardeen–Cooper–Schrieffer (BCS) condensation below a critical temperature. In the BCS condensation state, bare atoms with opposite wave vectors are bound into pairs, and unpaired bare atoms are transformed into a new kind of quasi-particles, i.e. the dressed atoms. The atom-pair system is a condensate or a superfluid and the dressed-atom system is a normal fluid. The critical temperature and the effective mass of dressed atoms are derived analytically. The transition from the BCS condensation state to the normal state is a first-order phase transition.
[1] Anderson M H, Ensher J R, Matthews M R, Wieman C E and Cornell E A 1995 Science 269 198
[2] Davis K B, Mewes M O andrews M R, van Druten N J, Durfee D S, Kurn D M and Ketterle W 1995 Phys. Rev. Lett. 75 3969
[3] Bradley C C, Sackett C A, Tollett J J and Hulet R G 1995 Phys. Rev. Lett. 75 1687
[4] Pethick C J and Smith H 2008 Bose-Einstein Condensation in Dilute Gases (Cambridge: Cambridge University)
[5] Pitaevskii Lev and Stringari Sandro 2003 Bose-Einstein Condensation (Oxford: Oxford University)
[6] Greiner M, Mandel O, Esslinger T, Hänsch T W and Bloch I 2002 Nature 415 39
[7] Shin Yong-il, Schunck C H, Schirotzek A and Ketterle W 2008 Nature 451 689
[8] Lin C Y, Lee D S and Rivers R J 2009 Phys. Rev. A 80 043621
[9] Lewenstein M and You L 1996 Phys. Rev. A 53 909
[10] Pollack S E, Dries D, Junker M, Chen Y P, Corcovilos T A and Hulet R G 2009 Phys. Rev. Lett. 102 090402
[11] Roberts J L, Claussen N R, Cornish S L, Donley E A, Cornell E A and Wieman C E 2001 Phys. Rev. Lett. 86 4211
[12] Beliaev S T 1958 Soviet Phys. JETP 7 289
[13] Fetter A L and Walecka J D 1971 Quantum Theory of Many-Particle Systems (New York: McGraw-Hill) p 316
[14] Callaway J 1991 Quantum Theory of the Solid State second edn (New York: Academic Press) p 720
2011, Vol. 28 
