  We revisit the problem of a single hole moving in the background of the two
dimensional Heisenberg antiferromagnet. The hole is loosely bound by an
impurity potential. We show that the bound state is generically a parity
doublet: there are parametrically close bound states of opposite parity. Due to
the degeneracy the bound state readily breaks local symmetries of the square
lattice and this leads to formation of the long range spiral distortion of the
antiferromagnetic background. A direct analogy with van der Waals forces in
atomic physics is discussed.
