INFLUENCE OF SPIN FLUCTUATIONS IN THE GROUND-STATE ON THE COHERENT MOTION OF HOLES IN HIGH-TC SUPERCONDUCTORS

The coherent two-dimensional motion of a hole generated in a high-Tc superconductor at half-filling is discussed. The system is described by the t-J model which reduces to the Heisenberg antiferromagnet (HAF) at half-filling. Special attention is payed to the influence of spin fluctuations in the ground state on the hole motion. Spin fluctuations can be considered as deviations of the true ground state of the Heisenberg antiferromagnet from the Néel state. The calculations are based on the introduction of a new trial wave function. It generalizes a wave function which was originally proposed by Shraiman and Siggia for the hole motion in the Néel state. As a result, we find that the excitation energy for the hole has a bandwidth which is reduced by a factor 0.7 as compared to the case without spin fluctuations. Moreover, the dispersion relation contains cubic harmonics which are due to effective hopping processes to more distant than second-or third-nearest neighbors. For larger values of the ratio t/J the band is substantially deformed. We compare our theory with results obtained from the exact diagonalization of finite clusters and find good agreement. © 1990 Springer-Verlag.