Inhomogeneous spin structures in high-Tc cuprates

We investigate inhomogeneous spin structures in the CuO2 planes of the high-Tc cuprates in the low doping regime. Within the theory of microscopic percolative phase separation a spin-polarized stripe in the (11) direction is examined as a simple example for a open-quote open-quote percolative close-quote close-quote subsystem. It turns out that for a certain stripe concentration range, a hole confined to this one-dimensional subsystem has a lower energy than an isolated spin-polaronic state. The coherent-potential approximation is used to obtain the density of states for more general spin-polarized configurations. This approach allows for the description of the insulator-metal transition in terms of a phase separated model, where besides the metallic phase, a nonvanishing antiferromagnetic order parameter is retained. copyright 1996 The American Physical Society