Impurity spin coupled to a strongly correlated electron system: Ground-state properties.

Exact results are provided for the ground state properties of an impurity spin coupled to a conducting band of strongly correlated electrons described by a t-J model. The ground states are proved to be unique, apart from the spin rotational degeneracy, and the ground state spins are found in the following case: (1) J = 0, one hole hopping on a lattice in dimensions d ≥ 2. (2) J 6= 0, arbitrary number of holes hopping on a one dimensional lattice, i.e., a Luttinger liquid interacting with a localized impurity spin.