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 q uantum Monte Carlo loop algorithm. The spin spin correlation functions exhi bit 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 thre e gapless modes of velocity pi/2. The physical implications of these result s are discussed.