Nature of carriers in one-dimensional correlated electron systems

Electron densities at the edge site in one-dimensional Hubbard model and t-J model are studied by using the Bethe ansatz solutions and exact diagonalization method. It is found that the boundary is electron-attractive, or equivalently hole-repulsive, near half-filling. We propose a new criterion to determine whether the carriers in a strongly correlated system are electron-like or hole-like depending on the electronic behavior at the boundary.