Topological phases of the bilinear-biquadratic spin-1 chain with single-ion anisotropy

Zakaria Jouini (EPFL)

Since Haldane’s prediction of a finite spin gap in integer-spin chains, the spin-1 chain has served as a paradigmatic model of quantum magnetism. Beyond the Heisenberg interaction, the most general SU(2)-invariant model includes a biquadratic interaction, often completed by an on-site anisotropy, typical of spin-1 ions in solids.

In this talk, I will present an approach combining bosonization and Bethe ansatz to show that dominant biquadratic interactions in the presence of an on-site anisotropy stabilize a gapped topological phase, in a region of the phase diagram previously identified by numerical studies as critical with central charge c=2. I will argue that this phase is a new realization of the Haldane phase in the spin-1 chain, characterized by hidden quadrupolar order, and I will discuss the prospects and implications for its experimental realization.

Contact : N. Laflorencie