  Based on an effective model of a doped antiferromagnetic Mott insulator, we
show that a doped hole will induce a dipole-like spin configuration in a spin
ordered phase at low doping. The kinetic energy of doped holes is severely
frustrated and a hole-dipole object is actually localized or self-trapped in
space. Without a balance from the kinetic energy, the long-range dipole-dipole
interaction between doped holes will dominate the low-energy physics, leading
to an inhomogeneity instability as hole-dipoles collapse into stripes. Both
antiphase metallic stripes of quarter-filling and antiphase insulating stripes
along a diagonal direction are discussed as composed of hole-dipoles as
elementary building blocks. Stripe melting and competing phases are also
discussed.
