SU(4) spin-orbit critical state in one-dimension
Abstract
Effect of quantum fluctuations concerned with the orbital degrees of freedom is discussed for the model with SU(4) symmetry in one-dimension. An effective Hamiltonian is derived from the orbitally two-fold degenerate Hubbard model at quarter filling. We numerically determine the ground state energy and the excitation spectrum and find that this system is gapless in consistent with the Bethe-ansatz results. We also find that the spin-spin correlation function shows a power-law behavior with four site period; < {\vec{S}}_{i} \cdot {\vec{S}}_{i+j} >_{bulk} \sim \cos(\pi j/2)/j^{\alpha}, where \alpha = 1.5 \sim 2.0 . The couplings between the spin and orbital fluctuations lead to the quantum critical state which is characterized by the gapless modes at q=\pi/2 belonging to the [2^{1}1^{2}] irreducible representation.Keywords
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