Mechanism of formation of half-doped stripes in underdoped cuprates

Using a variational Monte Carlo approach with a recently proposed stripe wave function, we showed that the strong correlation included in a t-J-type model has essentially all the necessary ingredients to form these stripes with modulations of charge density, spin magnetization, and pair field. If a perturbative effect of electron-phonon coupling to renormalize the effective mass or the hopping rate of holes is considered with the model, we find the half-doped stripes, which has on the average one half of a hole in one period of charge modulation, to be most stable energetic wise in the underdoped region, 1/12 <=delta <= 1/8. This is in good agreement with the observation in the neutron-scattering experiments. We also find long-range Coulomb interaction to be less effective in the formation of half-doped stripes.