Multicritical deconfined quantum-criticality and Lifshitz point of a helical valence-bond phase

Bowen Zhao, Jun Takahashi, Anders W. Sandvik

The $S=1/2$ square-lattice $J$-$Q$ model hosts a deconfined quantum phase transition between antiferromagnetic and dimerized (valence-bond solid) ground states. We here study two d…