First-order N\'eel-cVBS transition in a model square lattice $S=1$ antiferromagnet

Understand

We study the N\'eel to four-fold columnar valence bond solid (cVBS) quantum phase transition in a sign free $S=1$ square lattice model.

• This is the same kind of transition that for $S=1/2$ has been argued to realize the prototypical deconfined critical point.
• Extensive numerical simulations of the square lattice $S=1/2$ N\'eel-VBS transition have found consistency with the DCP scenario with no direct evidence for first order behavior.
• In contrast to the $S=1/2$ case, in our quantum Monte Carlo simulations for the $S=1$ model, we present unambiguous evidence for a direct conventional first-order quantum phase transition.