[1] Greiner M, Mandel O, Esslinger T, Hansch T W and Bloch I
2002 Nature 415 39

[2] Orzel C, Tuchman A K, Fenselau M L, Yasuda M and Kasevich M A
2001 Science 291 2386

[3] Morsch O and Oberthaler M 2006 Rev. Mod. Phys. 78 179

[4] Ji X M, Lu J F, Mu R W and Yin J P 2006 Acta Phys. Sin.
55 3396 (in Chinese)

[5] Xu Z J, Cheng C and Xiong H W 2003 Chin. Phys. Lett.
20 611

[6] Fisher M P A, Weichman P B, Grinstein G and Fisher D S 1989
Phys. Rev. B 40 546

[7] Altman E and Auerbach A 2002 Phys. Rev. Lett. 89
250404

[8] Li Z D, He P B, Li L, Liang J Q and Liu W M 2005 Phys.
Rev. A 71 053611

[9] Xie Z W, Zhang W P, Chui S T and Liu W M 2004 Phys. Rev.
A 69 053609

[10] Y J Jee, K J B Lee and Schlottmann P 1989 Phys. Rev. B
39 2815

[11] Stoferle T, Moritz H, Schori C, Kohl M and Esslinger
T 2004 Phys. Rev. Lett. 92 130403

[12] Wen X G 2002 Phys. Rev. B 65 165113