Spin waves in a doped antiferromagnet

Spin waves are studied in the t-J model for low dopant concentrations on the basis of a Green’s-function formalism in a slave-fermion Schwinger boson representation. The self-consistent Born approximation is used to calculate the Green’s function for holes. Both the coupling of spin waves to electron-hole pair excitations and the scattering of spin waves by holes are taken into account in calculating the Green’s function for spin waves. The spin-wave velocity is evaluated for various values of J/t. For small values of J/t, it is found to be strongly renormalized due to the creation of electron-hole pairs.