Entropy driven dimerization in a one-dimensional spin-orbital model

Abstract

We study a version of the one-dimensional spin-orbital model with spins $S=1\mathrm{}$ relevant to cubic vanadates. At small Hund’s coupling $J_H$ we discover dimerization in a pure electronic system solely due to a dynamical spin-orbital coupling. Above a critical value $J_H,$ a uniform ferromagnetic state is stabilized at zero temperature. More surprisingly, we observe a temperature driven dimerization of the ferrochain, which occurs due to a large entropy released by dimer states. This dynamical dimerization seems to be the mechanism driving the peculiar intermediate phase of ${\mathrm{YVO}}_3.$