A tunable quantum spin chain with three-body interactions

We present results for a spin chain model that interpolates between the conventional quantum Heisenberg spin chain (two-body interaction) in the limit of ferromagnetic and antiferromagnetic coupling. In this model, there is a special tuning point at which the model corresponds to the recently introduced, exactly solvable Fredkin spin chain (with its three-body interaction). We solve for the low-energy properties, numerically and semi-analytically, in order to track the properties of the system as it is tuned between the extreme limits and compare our results with the known values at the Fredkin point. We identify a zero-temperature phase diagram with multiple transitions and unexpected ordered phases.