31p-BD-11 ランダム場における Transverse Ising System II

健一 山口, 亘 木名瀬, 貴男 朴

仁 浅川, Masuo Suzuki

徹 池上, 精二 宮下

敬人 金吉, 幾夫 田村, Enaldo F. Sarmento

E. Cuevas

Abstract Some properties of d‐dimensional disordered models with long‐range random hopping amplitudes are investigated numerically at criticality. We concentrate on the correlation dimension d2 (for d = 2) and the nearest level spacing distribution Pc(s) (for d = 3) in both the weak (bd ≫ 1) and the strong (bd ≪ 1) coupling regime, where the parameter b− d plays the role of the coupling constant of the model. It is found that (i) the extrapolated values of d2 are of the form d2 = cdbd in the strong coupling limit and d2 = d − ad/bd in the case of weak coupling, and (ii) Pc(s) has the asymptotic form Pc(s) ∼ exp (−Adsα) for s ≫ 1, with the critical exponent α = 2 − ad/bd for bd ≫ 1 and α = 1 + cdbd for bd ≪ 1. In these cases the numerical coefficients Ad, ad and cd depend only on the dimensionality. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Carla Buzano, Mario Rasetti, M. Vadacchino

The transverse-field Ising model is solved within the scheme of the generalized mean-field method earlier proposed by the authors. The uncompatibility between the self-consistency condition and the thermal equilibrium is corrected through the introduction of a correlated mean-field, realized by a virtual-field parameter. Numerical results are discussed in detail, from which the specific heat and the transverse-field/critical-temperature phase boundary diagram are derived.