Spin waves and static susceptibility in the weakly doped t-J model



We investigate the spin dynamics in weakly doped high-temperature superconductors. The system is described by the two-dimensional t-J model. Our focus is on the interaction between mobile holes and spin waves. The calculations are based on a recently introduced cumulant method for computing the ground state energy of correlated electronic systems. Contrary to previous works using dynamical quantities like correlation functions or spectral densities our approach contains a static view to the system. This new method treats spin and hole dynamics on the same basis and allows for the calculation of static and dynamical quantities. We present results for spin-wave energies and transverse static susceptibilities for small hole concentrations and various values of t/J. We find a strong renor-malization of the spin-wave energies due to the spin-hole interaction. In agreement with neutron scattering experiments the spin-wave velocity vanishes at a critical hole density of a few percent which is equivalent to the instability of the antiferromagnetic order.