Model for frustrated spin-orbital chains as applied toCaV2O4

Abstract

Motivated by recent interest in quasi-one-dimensional compound ${\text{CaV}}_{2}{\text{O}}_{4}$, we study the ground states of a spin-orbital chain characterized by an Ising-like orbital Hamiltonian and frustrated interactions between $S=1$ spins. The on-site spin-orbit interaction and the Jahn-Teller effect compete with intersite superexchange leading to a rich phase diagram in which an antiferro-orbital phase is separated from the orbital paramagnet by a continuous Ising transition. Two distinct spin liquids depending on the underlying orbital order are found in the limit of small spin-orbit coupling. In the opposite limit, the zigzag chain behaves as a spin-2 chain with Ising anisotropy. The implications for ${\text{CaV}}_{2}{\text{O}}_{4}$ are discussed.