A dimensionless Hamiltonian of an N-spin Ising model without an external magnetic field (Fig. 1a) is given by Figure 1: Ising model and set-up for generating artificial Ising spins based on DOPOs.

This is the last in a series of three papers on the history of the Lenz-Ising model from 1920 to the early 1970s. In the first paper, I studied the invention of the model in the 1920s, while in the ...