Following the work of Canright, Girvin and Brass [Phys. Rev. Lett. 63 (1989) 2291], we scrutinize the fermionic mean-field theory for the two-dimensional s = 1/2 XY spin model of hard-core bosons. Using nonlocal vertex operators and fermion correlators in a constant magnetic field, we calculated the spin-spin correlations, which show a Bose condensation. The mean-field theory is appropriate not only for the ground state but also for the low-lying excited states.
机构:
Univ Michigan, Dept Phys, Ann Arbor, MI 48109 USA
Tsinghua Univ, IIIS, Ctr Quantum Informat, Beijing 100084, Peoples R ChinaUniv Michigan, Dept Phys, Ann Arbor, MI 48109 USA
Chan, Y-H
Duan, L-M
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机构:
Univ Michigan, Dept Phys, Ann Arbor, MI 48109 USA
Tsinghua Univ, IIIS, Ctr Quantum Informat, Beijing 100084, Peoples R ChinaUniv Michigan, Dept Phys, Ann Arbor, MI 48109 USA