arXiv:1401.6342 · Physical Review B
Zero-temperature spin-glass–ferromagnetic transition: Scaling analysis of the domain-wall energy
Cécile Monthus, Thomas Garel
Abstract
For the Ising model with Gaussian random coupling of average ${J}_{0}$ and unit variance, the zero-temperature spin-glass--ferromagnetic transition as a function of the control parameter ${J}_{0}$ can be studied via the size-$L$-dependent renormalized coupling defined as the domain-wall energy ${J}^{R}(L)\ensuremath{\equiv}{E}_{\text{GS}}^{(\text{AF})}(L)\ensuremath{-}{E}_{\text{GS}}^{(\text{F})}(L)$ (i.e., the difference between the ground-state energies corresponding to antiferromagnetic and ferromagnetic boundary conditions in one direction). We study numerically the critical exponents of this zero-temperature transition within the Migdal-Kadanoff approximation as a function of the dimension $d=2,3,4,5,6$. We then compare with the mean-field spherical model. Our main conclusion is that in low dimensions, the critical stiffness exponent ${\ensuremath{\theta}}^{c}$ is clearly bigger than the spin-glass stiffness exponent ${\ensuremath{\theta}}^{\text{SG}}$, but that they turn out to coincide in high enough dimension and in the mean-field spherical model. We also discuss the finite-size scaling properties of the averaged value and of the width of the distribution of the renormalized couplings.