Seeking the spin-glass state in a field through windows

Although the presence of a finite-temperature transition in the three-dimensional Ising spin-glass is well established in zero field, the behavior in the presence of an external magnetic field has been a matter of long-standing controversy. For the infinite-range Sherrington-Kirkpatrick spin glass, mean-field theory predicts a transition line known as Almeida-Thouless (AT) line that separates the paramagnetic and spin-glass phases in the temperature-field plane. Despite extensive numerical efforts, no consensus has been reached with regard to the presence of an AT line in short-range systems, mostly due to strong corrections to finite-size scaling. Here we investigate the transition in a three-dimensional system via a method in which we perform population annealing Monte Carlo simulations for a large system, but only consider the thermodynamic properties of the system restricted to a small window. By computing the wave-vector-dependent spin-glass susceptibility for the individual windows, as well as for the whole system, we investigate the effects of finite-size corrections to the two-point correlation function.