Minchul Lee, Eun-Ah Kim, Jong Soo Lim, M. Y ChoiPhys. Rev. B. 69, 115117. DOI: http://dx.doi.org/10.1103/PhysRevB.69.115117. arXiv:cond-mat/0402024 Monday, March 22, 2004 PhysRevB2004Lee-1.pdf