A new method to calculate the spin-glass order parameter of the two-dimensional ±J Ising model

A new method to numerically calculate the nth moment of the spin overlap of the two-dimensional +/-J Ising model is developed using the identity derived by one of the authors (HK) several years ago. By using the method, the nth moment of the spin overlap can be calculated as a simple average of the nth moment of the total spins with a modified bond probability distribution. The values of the Binder parameter etc have been extensively calculated with the linear size, L, up to L = 23. The accuracy of the calculations in the present method is similar to that in the conventional transfer matrix method with about 10(5) bond samples. The simple scaling plots of the Binder parameter and the spin-glass susceptibility indicate the existence of a finite-temperature spin-glass phase transition. We find, however, that the estimation of T-c is strongly affected by the corrections to scaling within the present data (L less than or equal to 23). Thus, there still remains the possibility that T-c = 0, contrary to the recent results which suggest the existence of a finite-temperature spin-glass phase transition.