Emergence of the XY-like phase in the deformed spin-3/2 AKLT systems

Understand

Affleck, Kennedy, Lieb and Taski (AKLT) constructed an exemplary spin-3/2 valence-bond solid (VBS) state on the hexagonal lattice, which is the ground state of an isotropic quantum antiferromagnet and possesses no spontaneous magnetization but finite correlation length.

• This is distinct from the N\'eel ordered state of the spin-3/2 Heisenberg model on the same lattice.
• Niggemann, Kl\"umper and Zittartz then generalized the AKLT Hamiltonian to one family invariant under spin rotation about the z-axis.
• The ground states of this family can be parameterized by a single parameter that deforms the AKLT state, and this system exhibits a quantum phase transition between the VBS and N\'eel phases, as the parameter increases from the AKLT point to large anisotropy.