ISSN:
1434-6036
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Physik
Notizen:
Abstract We re-examine the random-phase approximation (RPA) in the antiferromagnetic spin-density-wave state of the half-filled square lattice repulsive Hubbard model. It is shown that forU/t≪1 the RPA yields a vanishing spinwave velocity, ħc∼(2πt)−1(U/t)1/2, a diverging uniform transverse susceptibility,χ ⊥∼(2πt)−1(U/t −1/2, and a constant spin stiffness,ρ s ∼2πt)−2 t. The behavior ofρ s shows that the RPA cannot be correct in the weak coupling regime, becauseρ s should vanish in the limitU/t→0. We give a formally exact expression forρ s and identify the term which is neglected within the RPA.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01318167
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