Abstract
We consider modified
t−J
model with minimum of single-hole dispersion at the points
(0,±π)
,
(±π,0)
. It is shown that two holes on antiferromagnetic background produce a bound state which properties strongly differs from the states known in the unmodified
t−J
model. The bound state is d-wave, it has four nodes on the face of the magnetic Brillouin zone. However, in the coordinate representation it looks like as usual s-wave.