  We investigate the phase diagram and the spin-orbital entanglement of a
one-dimensional SU(2)$\otimes XXZ$ model with SU(2) spin exchange and
anisotropic $XXZ$ orbital exchange interactions and negative exchange coupling.
As a unique feature, the spin-orbital entanglement entropy in the entangled
ground states increases here linearly with system size. In the case of Ising
orbital interactions we identify an emergent phase with long-range spin-singlet
dimer correlations triggered by a quadrupling of correlations in the orbital
sector. The peculiar translational invariant spin-singlet dimer phase has
finite von Neumann entanglement entropy and survives when orbital quantum
fluctuations are included. It even persists in the isotropic
SU(2)$\otimes$SU(2) limit. Surprisingly, for finite transverse orbital coupling
the long-range spin singlet correlations also coexist in the antiferromagnetic
spin and alternating orbital phase making this phase also unconventional.
Moreover we also find a complementary orbital singlet phase that exists in the
isotropic case but does not extend to the Ising limit. The nature of
entanglement appears essentially different from that found in the frequently
discussed model with positive coupling. Furthermore we investigate the
collective spin and orbital wave excitations of the disentangled
ferromagnetic-spin/ferro-orbital ground state and explore the continuum of
spin-orbital excitations. Interestingly one finds among the latter excitations
two modes of exciton bound states. Their spin-orbital correlations differ from
the remaining continuum states and exhibit logarithmic scaling of the von
Neumann entropy with increasing system size.
