Effect of the orbital level difference in doped spin-1 chains

The doping of a two-orbital chain with mobile S = 1/2 fermions and strong H und's rule couplings stabilizing the S = 1 spins strongly depends on the pr esence of a level difference among these orbitals. Using density matrix ren ormalization group (DMRG) methods, we find a finite spin gap upon doping an d dominant pairing correlations without level difference, whereas the prese nce of a level difference leads to dominant charge density wave (CDW) corre lations with gapless spin-excitations. The string correlation function also shows qualitative differences between the two models.