Thermodynamics of the One-Dimensional SU(4) Symmetric Spin-Orbital Model

The ground-state properties and thermodynamics of the one-dimensional SU(4) symmetric spin system with orbital degeneracy are investigated using the quantum Monte Carlo loop algorithm. The spin-spin correlation functions exhibit a 4-site periodicity, and their low-temperature behavior is controlled by two correlation lengths that diverge like the inverse temperature, while the entropy is linear in temperature and its slope is consistent with three gapless modes of velocity $\pi /2$. The physical implications of these results are discussed.