CURRENT CARRIERS IN A QUANTUM 2-DIMENSIONAL ANTIFERROMAGNET

The interaction of current carriers with localized moments in a two-dimensional Heisenberg antiferromagnet is considered in the s-d exchange model (both using perturbation theory and in the limit of infinitely large s-d parameter) and in the t-J model. It is demonstrated that at low T << J the electron spectrum has the same structure as in the ground state despite the absence of long-range magnetic order. The influence of spin dynamics on the manifestations of the Kondo effect is investigated, and the corresponding T-linear term in resistivity is obtained. The problem of the formation of a narrow quasi-particle peak near the band bottom due to spin dynamics is discussed. Using the Schwinger boson or Dyson-Maleev representation yields, unlike the linear magnon theory, an appreciable bare band-width of a hole in the t-J model, which is proportional to the sublattice magnetization quantum contraction.